Question

If s(x) = 2 – x2 and t(x) = 3x, which value is equivalent to (s t)(-7)?

a. -439
b. -141
c. 153
d. 443

Answer 1

Answer: a. -439

Explanation:

Given:
`s(x)=2-x^2\text{ and }t(x)=3x`

Now, the composite function is given by :

`s\circ t(x)\\\\=s(t(x))\\\\=s(3x)\\\\=2-(3x)^2\\\\=2-9x^2`

Now, put the value of x = -7, we get

`s\circ t(-7)\\\\=s(t(-7))\\\\=2-9(-7)^2\\\\=2-9(49)\\\\=−439`

Hence the value equivalent to
`s\circ t(-7)\text{ is }−439`.

Answer 2

s(x) = 2 - x^2
t(x) = 3x
(s o t)(x) = s(t(x)) = 2 - (3x)^2 = 2 - 9x^2
(s o t)(-7) = 2 - 9(-7)^2 = 2 - 9(49) = 2 - 441 = -439