Remembering

Use Simplify and Expand:
expr := (x + 2)^2 - (x - 3)^2[br][br]Simplify[expr][br][br]Expand[expr][br][br]
Factor and verify:
Factor[x^2 + 5x + 6][br][br]Expand[(x + 2)(x + 3)][br][br]
Substitute into expressions:
Substitute[f(x), x = x + 1][br][br]Substitute[f(x), x = g(x)]
– Mathías Tejera

Information: Remembering