Question

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

Answer 1

For this case we have the following functions:
 $s (x) = 2-x ^ 2 t (x) = 3x$
 When multiplying the functions we have:
 $(s * t) (x) = s (x) * t (x)$
 Substituting values we have:
 $(s * t) (x) = (2-x ^ 2) * (3x)$
 Rewriting we have:
 $(s * t) (x) = 6x - 3x ^ 3$
 We evaluate the new function for x = -7
 $(s * t) (-7) = 6 (-7) - 3 (-7) ^ 3 (s * t) (-7) = -42 - 3 (-343) (s * t) (-7) = -42 + 1029 (s * t) (-7) = 987$
 Answer:
 A value that is equivalent to (s • t) (-7) is:
 $(s * t) (-7) = 987$

Answer 2

The given functions are
s(x) = 2 - x²
t(x) = 3x

By multiplying the both functions

∴ (s * t ) (x) = (2-x²) * (3x) = 6x - 3x³

To find (s * t ) (-7), substitute with x = -7 in the resultant function of the multiplication

∴ (s * t ) (-7) = 6 * (-7) - 3* (-7)³ = 987