Question

Which expression is equal to (f + g)(x)?

Answer 1

ANSWER

B.

$(f + g)(x) = {x}^{3} + x- 715$

EXPLANATION

The given functions are:

$f(x) = \sqrt{ {x}^{2} + 28x + 196}$

This is the same as

$f(x) = \sqrt{ {(x + 14)}^{2} }$

$f(x) = x + 14$

and

$g(x) = {x}^{3} - 729$

$(f + g)(x) = f(x) + g(x)$

$(f + g)(x) = x + 14 + {x}^{3} - 729$

$(f + g)(x) = {x}^{3} + x- 715$

The correct answer is B

Answer 2

Answer:

B.

Step-by-step explanation:

$= f(x) + g(x)\\= \sqrt{x^{2} +28x+196} +x^{3} -729\\factor (x^{2} +28x+196) to ((x+14)^{2})\\= \sqrt{(x+14)^{2} } +x^{3} -729\\= x+14+x^{3} -729\\=x^{3} +x-715$