bjr
(7x+5)²+(3x+3)(7x+5)
1) développer
(7x+5)²+(3x+3)(7x+5) = (7x)² + 7*2x*5 + 25 + 21x² +15x +21x + 15
= 49x² + 70x + 25 + 21x² + 36x + 15
= 49x² + 21x² + 70x + 36x + 25 + 15
= 70x² + 106x + 40
2) factoriser
(7x+5)²+(3x+3)(7x+5) = (7x + 5)(7x + 5) + 3x + 3)(7x + 5)
= (7x + 5) (10x + 8)
= (7x + 5)*2(5x + 4)
= 2(7x + 5)(5x + 4)
