Problem: If f(x)=2x(x−1)​, then f(x+2) equals:
Answer Choices:
A. f(x)+f(2)
B. (x+2)f(x)
C. x(x+2)f(x)
D. x+2xf(x)​
E. x(x+2)f(x+1)​
Solution:
​f(x+2)=(x+2)(x+2−1)/2 and f(x+1)=(x+1)(x+1−1)/2.​
So (x+1)/2=f(x+1)/x;∴f(x+2)=(x+2)f(x+1)/x.