need help with functions

Question

Is f(x)=2-5x^2 correct when

f(root of 2) - f(1)=-5

Answer 1

f(x) = 2 - 5x²

 

f(√2) = 2 - 5(√2)² = 2 - 10 = -8

 

f(1) = 2 - 5(1)² = 2 - 5 = -3

 

So, f(√2) - f(1) = -8 - (-3) = -5