Answer:
k = 13
Step-by-step explanation:
substitute x = x + 5 into f(x) , that is
f(x + 5) = (x + 5)² + 3(x + 5) - 10 ← expand squared factor using FOIL
= x² + 10x + 25 + 3x + 15 - 10
= x² + 13x + 30
compare this with f(x + 5) = x² + kx + 30
for the 2 expressions to be equal , then k = 13
