Equivalent expressions

Question

Tim wrote the expressions g^2-2gh-h^2 and -g(g+2h-1)-h^2

Greg substituted 0 for g and 1 for h and said the expressions are equivalent. Is he correct??

Explain.

Answer 1

The two expressions are not equivalent. However, if you evaluate them both at g=0 and h=1, they happen to give the same value, but that is not the same as being equivalent.