Réponses

2014-03-06T12:05:21+01:00
(2x-7)²-(5-x)²
=[(2x-7)²]-[(5-x)²]
=[4x²-28x+49]-[25-10x+x²]
=4x²-28x+49-25+10x-x²
= 3x² - 18x + 24