Bonsoir,
(3x+5)² = 9x² +30x +25
(3x+5) ( 2x+7) =
6x² +21x +10x +35 = 6x² +31x +35
9x² +30x +25 - ( 6x² +31x +35)=
9x² +30x +25 - 6x² -31x -35 = 3x² -x -10
2)
(3x+5) ( 3x+5 -2x-7) =
(3x+5) ( x -2)
3)
x=2
3x² -x -10 = 3*4 -2 -10 = 0
x= 0
3x² -x -10 = 0-0 -10 = -10
x= -5/3
3x² -x -10 =
(-5/3) ² -5/3 -10 =
25/9 -5/3 -10=
25/9 - 15/9 - 90/9 = -80/9
