Answer:
(a) (2x +7), (x -4)
(b) (-7/2, 0), (4, 0)
Step-by-step explanation:
(a)
When looking for integer factors of a quadratic of the for ax² +bx +c = 0, it is useful to start by looking for factor pairs whose product is a·c and whose sum is b.
Here, that means you're examining the factors of 2·(-28) = -56, and looking for a pair that have a sum of -1. We can start by examining the ways that -56 can be factored:
-56 = -56(1) = -28(2) = -14(4) = -8(7)
Sums of these factor pairs are -55, -26, -10, -1, so it is the last pair we're interested in.
At this point, you can rewrite the x-term using these factors and then factor the quadratic by pairs.
2x² -8x +7x -28 = 0 . . . . . . . use -x = -8x+7x
(2x² -8x) +(7x -28) = 0 . . . . group into pairs of terms
2x(x -4) +7(x -4) = 0 . . . . . . factor each pair of terms
(2x +7)(x -4) = 0 . . . . . . . . . the factored equation
The factors of this equation are (2x +7) and (x -4).
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(b)
The x-intercepts are the values of x that make the factors zero.
2x +7 = 0 . . . looking for x that makes the first factor zero
2x = -7 . . . . . subtract 7
x = -7/2 . . . . divide by the coefficient of x
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x -4 = 0 . . . . looking for x that makes the second factor zero
x = 4 . . . . . . add 4
The x-intercepts are x = -7/2 and x = 4.
