Sagot :
Bonjour,
(3x-5)²-(2x+3)(4x-5) = 9x²-30x+25-(8x²-10x+12x-15)
= 9x²-8x²-30x+10x-12x+25+15
= x²-32x+40
(4x-3)²-(4x-3)(2x+1) = (4x-3)(4x-3)-(4x-3)(2x+1)
= (4x-3)[(4x-3)-(2x+1)]
= (4x-3)(2x-4)
= 2(4x-3)(x-2)
9x²-30x+25 = (3x-5)²
A=(9x^2-30x+25)-(8x^2-10x+12x-15)
=9x^2-30x+25-8x^2+10x-12x+15
= x^2-32x+40
B=(4x-3)^2-(4x-3)(2x+1)
=(4x-3)((4x-3)-(2x+1))
=(4x-3)(4x-3-2x-1)
=(4x-3)(2x-4)
=(4x-3)2(x-2)
C=9x^2-30x+25
=(3x-5)^2