If f(x)=4x-x2, x ∈ R, then f (a+1)-f (a-1) is equal to

Question

If f(x)=4x-x2, x ∈ R, then f (a+1)-f (a-1) is equal to (A) 2(4-a) (B) 4(2-a) (C) 4(2+a) (D) 2(4+a)

Tardigrade Admin · Accepted Answer

f (a+1)-f (a-1) =[4(a+1)-(a+1)2]-[4(a-1)-(a-1)2] =8-4a=4(2-a).

Q. If $f (x) = 4 x - x^{2}, x \in R$ , then $f (a + 1) - f (a - 1)$ is equal to