Question

F(x)=-9x^2-2x and g(x)=3x^2+6x-9, find (f-g)(x) and (f-g)(-4)

Answer 1

Answer:

$(f-g)(x) = -12x^{2} - 8x + 9$

(f-g)(-4) = -151

Step-by-step explanation:

To find f-g(x) we subtract the common terms. So

$f(x) = -9x^{2} - 2x$

$g(x) = 3x^{2} + 6x - 9$

(f-g)(x)

$(f-g)(x) = f(x) - g(x) = -9x^{2} - 2x - (3x^{2} + 6x - 9) = -9x^{2} - 2x - 3x^{2} - 6x + 9 = (-9 - 3)x^{2} + (-2 - 6)x + 9 = -12x^{2} - 8x + 9$

(f-g)(-4)

$(f-g)(x) = -12x^{2} - 8x + 9$

We replace x by -4

$(f-g)(-4) = -12(-4)^{2} - 8(4) + 9= -151$

(f-g)(-4) = -151