Sagot :
ex2 :
c)(2x+5)(3x+7)
2x*3x+2x*7+5*3x+5*7
6x²+14x+15x+35
6x²+29x+35
d)(5x+8)(2x-7)
5x*2x+5x*(-7)+8*2x+8*(-7)
10x²-35x+16x-56
10x²-19x-56
e)(2x-5)(3x-2)
2x*3x+2x*(-2)-5*3x-5*(-2)
6x²-4x-15x+10
6x²-19x+10
f)(2+x)(5x-4)
2*5x+2*(-4)+x*5x+x*(-4)
10x-8+5x²-4x
5x²+6x-8
ex72 :
a)(2x+3)(4x+1)
2x*4x+2x*1+5*4x+3*1
8x²+2x+12x+3
8x²+14x+3
b)(3x-1)(2x+4)
3x*2x+3x*4-1*2x-1*4
6x²+14x-2x-4
6x²+12x-4
c)(5x+1)(2x-4)
5x*2x+5x*(-4)+1*2x+1*(-4)
10x²-20x+2x-4
10x²-18x-4
d)(2x-5)(4x-3)
2x*4x+2x*(-3)-5*4x-5*(-3)
8x²-6x-20x+15
8x²-26x+15
exercice n°2
C=(2x+5)(3x+7)
C=2x*3x+2x*7+5*3x+5*7
C=6xcarré+14x+15x+35 =6xcarré+29x+35
D=(5x-8)(2x-7)
5x*2x-5x*7-8*2x-(-8*7)=10x carré-35x-16x+56=10xcarré-51x+56
E=(2x-5)(3x-2)
2x*3x-2x*2-5*3x-(5*-2)=6xcarré-4x-15x+10=6xcarré-19x+10
F=(2x+5)(5x-4)
2x*5x-2x*4+5*5x-5*4=10xcarré-8x+25x-20=10xcarré+17x-20
n°72
A=(2x+3)(4x+1)
8xcarré+2x+12x+3=8xcarré+14x+3
B=(3x-1)(2x+4)
6xcarré+12x-2x-4=6xcarré+10x-4
C=(5x+1)(2x-4)
10xcarré-20x+2x-4=10xcarré-20x-4
D=(2x-5)(4x-3)
8xcarré-6x-20x+15=8xcarré-26x+150bonne chjance