Answer:
a.= 24 b.=-21 c. is x=-7 or 3
Step-by-step explanation:
a) f(5)= 5² + 4 x 5 -21
=24
b) f(0)= 0² + 4 x 0 -21
= -21
c) f(x)= 0
=> x² + 4x -21 =0
=> x = 3, x= -7
