Bonjour,
a) D'écloper et réduire:
(7x+9)²
= 49x² +126x +81
(3x-7)²
= 9x² +42x +49
(7x+3)(7x-3)
= 49x² -9
(3+7x)²
= 49x² +42x +9
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b) Factorise et réduit
25x²+70x+49
= (5x+7)²
81x²-54x+9
= (9x -3)²
81x²-9
= (9x-3) 9x+3)
9x²-49x²
= (3x-7x) ( 3x+7x)
(3x+5)²-(2x+9)²
= (3x+5) (3x+5) - (2x+9)(2x+9)
x²-10x+25
= (x-5)²
9+6x+2
= 3(3+2x) +2
1-x²
= (1-x) (1+x)
4x²+12x+9
= (2x+3)²
x²-16
= (x-4) (x+4)