Question

if f(x)=x-4x+6,find f(1)-f(-1)

Answer 1

here
f (x)=x-4x+6
when
x= 1
f (x) = x-4x+6
=1-4×1+6
=3
when
x=-1
f (x) = x-4x+6
= 3-4×3+6
= -3
now,
f (1)-f (-1) = 3-(-3)
= 6
so , f (1)-f (-1) is 6