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Two linear functions are combined with addition, and then the same two linear functions are combined by multiplication.

Which functions could be the result of the combinations? Select two options.
A. 16x – 12
B. 17x – 12
C. 72x2 – 96x
D. 72x2 + 108x
E. 72x2 – 204x + 144

User Codahk
by
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1 Answer

5 votes

Answer:

Explanation:

We can eliminate options C and D quite quickly because factoring either one would have one equation be y = x and the other either y = 72x - 96 or y = 72x + 108. Neither of these added to x will give either option A or B

so that leaves E.

72x² – 204x + 144 = 0

we can find the zeros

x = (204 ± √(204² - 4(72)(144))) / (2(72))

x = (204 ± 12) / 144

x = 1.5

x = 4/3

so the equation has factors

(x - 1.5)(x - 4/3)

and therefore also a factor in their product

x² - (
(17)/(6))x + 2

which is 1/72 of the original quadratic

so all factors of E are

72(x - 1.5)(x - 4/3)

now we need to distribute factors of 72 among the other two factors so that when we add them together the x¹ terms are either 16 or 17 and the x⁰ terms sum to -12. let "a" and "b" be the factors of 72.

ab = 72

a = 72/b

-1.5a - 4b/3 = -12

1.5a + 4b/3 = 12

1.5(72/b) + 4b/3 = 12

108/b + 4b/3 = 12

324/b + 4b = 36

324 + 4b² = 36b

81 + b² = 9b

b² - 9b + 81 = 0

b = (9 ±√(9² - 4(1)(81))) / 2(1))

b = (9 ± √-243) / 2

as both of these roots are imaginary numbers

there is no valid solution to this problem as posed

IF we allow a slight edit to answer B, we can factor 72 into 9•8

y = 8(x - 1.5) y = 9(x - 4/3)

y = 8x - 12 y = 9x - 12

so the sum of the two would be 17x - 24

User Sumithran
by
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