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

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

For this case we have the following functions:
 
 When multiplying the functions we have:
 
 Substituting values we have:
 
 Rewriting we have:
 
 We evaluate the new function for x = -7
 
 
 A value that is equivalent to (s • t) (-7) is: