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| | ANSWERS FOR THE REVIEW/TUTORIAL |
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| 1. | Answer | 5 |
| | Evaluate x2 3x + 9 for x = 1 |
| | When substituting x = 1 in x2 |
| | be sure to do the exponent before the multiplication by 1 |
| | | to get (1)2 = 1. So 1 3 + 9 = 5 |
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| 2. | Answer |  |
| | | When multiplying |  | so that | |
| | |  |
| | | becomes |  | |
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| 3. | Answer | 2(3x - y) |
| | | Using the distribute law -2(y - x) = -2y + 2x we get: |
| | 5x 2(y x) x |
| | = 5x 2y + 2x x |
| | = 6x -2y |
| | = 2(3x - y) |
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| 4. | Answer |  |
| | | To divide by 3, we invert and multiply |  | |
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| 5. | Answer |  |
| | Write the numerator as a single fraction with denominator of 4, |
| |  |
| | | and write the denominator as a single fraction with denominator of 6, |
| | |  |
| | | | Now | divide |  | by |  | |
| | Be sure to invert and multiply to get |
| | |  |
| | Here we divided the denominator 4 and the numerator 6 by 2. |
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| 6. | Answer |  |
| | ,  |
| | | |
| | | since x4 is positive. Similarly |  | |
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| 7. | Answer |  |
| | | Since |  | we write | |
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| 8. | Answer | 24x5y8 |
| | When multiplying exponent expressions with the same base, keep the |
| | | base and add the exponents thus, x3(x2) = x5 and y(y7) = y8 |
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| 9. | Answer |  |
| | Write the equation of the line in the form y = mx + b or where m is the slope. |
| | | 3y = 2x 10 |
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| 10. | Answer |  |
| | | Write |  | | and rationalize |  | | Now we are adding |  | |
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| 11. | Answer |  |
| | Multiply both sides of the equation by the denominator x 3 |
| |  |
| | | | Use the fact that |  | |
| | 1 3(x 3) = x |
| | 1 3x + 9 = x |
| | 10 = 4x |
| |  |
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| 12. | Answer | x = 5, x = 5 |
| | There are two values of x whose absolute value is 5 |
| | |-5| = 5 and |5| = 5 |
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| 13. | Answer |  |
| | We factor x2 3x = x(x 3) and 9 x2 = (3 x)(3 + x) |
| | Remember the difference of squares factorization a2 b2 = (a b)(a + b). |
| | | Thus we get |
| |  |
| | Use the fact that x – 3 = – (3 – x), so that |
| | |  |
| | Putting this together we get |
| | |  |
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| 14. | Answer | x < 6 |
| | 2x + 1 > 3x + 7 |
| | Subtract 3x from both sides x + 1 > 7 |
| | Subtract 1 from both sides x > 6 |
| | Multiply by 1, we get x < 6 |
| | Remember multiplying an inequality by a minus changes the sense of the arrow. |
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| 15. | Answer |  | and | x = 2 | |
| | Consider the standard quadratic equation ax2 + bx + c = 0, |
| | | whose solution is |  | |
| | For the solution of 2x2 + 3x 2 = 0, a = 2, b = 3, and c = 2. |
| | Since the discriminant b2 4ac = 32 4(2)( 2) = 9 + 16 = 25 is a |
| | perfect square, we can factor directly: 2x2 + 3x 2 = 0, |
| | (2x 1)(x + 2) = 0 |
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| |  | x = 2 | |
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| 16. | Answer |  |
| | For the solution of 2x2 3x 4 = 0, we have a = 2, b = 3, c = 4. |
| | The discriminant b2 4ac = ( 3)2 4(2)( 4) = 9 + 32 = 41 is not a |
| | perfect square so that we must use the quadratic formula and get |
| | | two real roots: |  | Thus | |
| |  |
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| 17. | Answer |  |
| | For the solution of 2x2 6x + 5 = 0, a = 2, b = 6, c = 5 |
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| | The discriminant b2 4ac = ( 6)2 4(2)( 5) = 36 40 = 4. |
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| | Since the discriminant is negative, the two roots are imaginary. |
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| | | Thus, here we use |  | |
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| | We can reduce the answer by factoring 2 in the numerator |
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| 18. | Answer |  |
| | The negative exponent means we have to take the reciprocal of what is in |
| | | the parentheses and then square. |  | |
| | Remember when raising a fraction to a power, both the denominator and |
| | numerator are raised to that power |
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| 19. | Answer | x = 3, y = 2 Solve for x and y there are two methods that are often used. |
| | Addition method: Multiply the second equation by 5 |
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| | 5x 3y = 21 |
| | 5x 25y = 35 |
| | Add the equations to get: |
| | 28y = 56 |
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| | | |
| | Substitute back into the second equation to get: |
| | x + 5( 2) = 7 |
| | x 10 = 7 |
| | x = 7 + 10 = 3 |
| | Thus x = 3, y = 2. |
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| | Substitution method: Solve for x in the second equation to get: |
| | x = 7 5y |
| | Substitute for x in the first equation to get: |
| | | | | 5(–7 – 5y) – 3y = 21 | | | –35 – 25y – 3y = 21 | | | –35 – 28y = 21 | | Add 35 | – 28y = 21 + 35 | | | – 28y = 56 | | | Divide by – 28 | | |  | |
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| | Substitute in equation two to get x. Substitute the value y = 2 |
| | in x = 7 5y to get x = 7 5(2) = 7 + 10 = 3 |
| | Thus x = 3, y = 2. |
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| 20. | Answer | Answer: 3 < x < 7 |
| | We can do the problem algebraically or geometrically. |
| | Algebraically: |
| | |x - 2| < 5 means 5 < x 2 < 5 |
| | So by adding to 2 all three parts of the inequality we get |
| | 5 < x 2 < 5 |
| | 5 + 2 < x 2 + 2 < 5 + 2 |
| | 3 < x < 7 |
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| | Geometrically: |
| | |x - 2| < 5 means that the distance (in both directions) from x to 2 is less than 5. |
| | So if we move 5 units to the right (up the axis) from 2 we get 7 and 5 units |
| | to the left (down the axis) from 2 we get 3 |
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| 21. | Answer |  |
| | | The least common denominator is xy. Thus |  | |
| | Since the denominators of the two fractions are now the same, |
| | we can add the numerators getting |
| |  |
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| 22. | Answer | (x 3)(x +3)(x2 + 9) |
| | Recall the factorization of the difference of squares a2 b2 = (a b)(a + b) |
| | x4 81 is a difference of squares namely (x2 )2 and 92. |
| | x4 81 = (x2 9)( x2 + 9). The first factor is again a difference of squares: |
| | (x2 9) = (x 3)(x +3) |
| | x4 81 = (x2 9)( x2 + 9) = (x 3)(x +3)(x2 + 9) |
| | x2 + 9, the sum of squares, does not factor |
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| 23. | Answer |  |
| | The least common denominator is 24y. |
| | | Thus |  | |
| | Here since the denominators are the same we add the numerator. |
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| 24. | Answer | The lines are parallel. |
| | If you solve for y in each equation to get the form y = mx + b, |
| | you can examine the slopes m and the y intercepts b. |
| | | Equation 1 becomes: |  | | Equation 2 becomes: |  | |
| | which reduces to |
| | |  |
| | Since the slopes are equal and the y intercepts are not, the lines are |
| | parallel. In the case that both the slopes and the y intercepts were equal, |
| | | the lines would be the same. |
| | | In the case that the slopes are unequal, the lines intersect in one point. |
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| 25. | Answer | 2 |
| | | Think of as |  | as |  | |
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| |  | is the cube root of 8 often written as |  | |
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| | | | So that |  | |
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| |  | the meaning of a negative exponent. | |
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| | |  | is the square root of 4 | |
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| | | often written |  | Thus |  | |
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| 26. | Answer | x < 2 or x > 3 |
| | x2 5x + 6 > 0 |
| | To find the solution set for x set the inequality equal to zero and factor and solve for x: |
| | x2 5x + 6 = 0 |
| | (x 3)(x 2) = 0 |
| | x = 3, x = 2 |
| | Since the inequality is strictly greater than zero, neither of these are in the solution set. |
| | These two numbers divide the x axis into three sections: |
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| | | ¥ < x < 2, | 2 < x < 3, | and 3 < x < ¥ | |
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| | Pick any "test" number for each section and substitute into the inequality: |
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| | For ¥ < x < 2, say x = 0. |
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| | Substituting x = 0 into x2 5x + 6 gives us (0)2 5(0) + 6 = 6 |
| | | which is greater than zero. |
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| | Thus ¥ < x < 2 is part of the solution set. |
| | | For 2 < x < 3, we can test with |  | or |  | |
| | | | Substituting |  | into x2 5x + 6 gives us |  | |
| | which is less than zero. |
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| | Thus 2 < x < 3, is NOT in our solution set. |
| | For 3 < x < ¥, we can substitute x = 4 to get |
| | | 42 5(4) +6 = 16 20 + 6 = 12 > 0. |
| | Thus 3 < x < ¥ is part of the solution set. |
| | Thus the complete solution set is {x| ¥ < x < 2 or 3 < x < ¥} |
| | which can also be written in interval notation as ( ¥, 2) (3, ¥). |
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| 27. | Answer | 28 |
| | If f(x) = x3 + 1, f(3) = 33 + 1 = 28 |
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| 28. | Answer | The horizontal line one unit above the x axis. |
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| 29. | Answer | The vertical line 3 units to the left of the y axis. |
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| 30. | Answer | The graph of 2x + 3y = 2 is |
| |  |
| | To graph 2x + 3y = 2, we need to find any two points which lie on the line |
| | and connect them with the straight edge. There are several ways to do this. |
| | | We outline two common methods. |
| | Intercept method: |
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| | | If we let x = 0, the y intercept is 3y = 2 or |  | |
| | | and if we let y =0 the x intercept is (1,0) |
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| | Slope-Intercept method: |
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| | | Solving for y in the form y = mx + b we get: |  | |
| | | From this form we see that the y intercept is |  | |
| | | From this point we can use the slope, which is |  | |
| | | to find a second point by moving, 2 units to the left (0 2 = 2) |
| | | | and 3 units up |  | to get the second point |  | |
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| | Close |