Mathematics for IGCSE & O level - Functions (Section 1 - No. 47)
If f(x) = x^2 -1, then which of the following is equal to f(x+h) - f(x)?
2xh+h^2
h^2+2h
2xh
h^2
คำอธิบาย
f(x+h)=(x+h)^2 -1. Then f(x+h)-f(x) = (x+h)^2 -1 - (x^2-1) = x^2+2xh+h^2-1-x^2+1 = 2xh+h^2