bjr
A(x) = 4x² - 100 = (2x)² - 10²
= (2x - 10) (2x + 10)
B(x) = (5+x) (1-2x) + (5+x) (1-3x)
= 5*1 + 5*(-2x) + x*1 + x*(-2x) + 5*1 + 5*(-3x) + x*1 + x*(-3x)
= 5 - 10x + x - 2x² + 5 - 15x + x - 3x²
= -5x² - 13x + 10
C(x) = (x-3)² = x² - 2*x*3 + 3² = x² - 6x + 9
A(x) = 0
(2x - 10) (2x + 10) = 0
soit 2x - 10 = 0 => x = 5
soit 2x + 10 = 0 => x = -5
A(x) = 69
A(x) = 4x² - 100 = 69
4x² - 169 = 0
(2x)² - 13² = 0
tu finis
B(x) = 0
(5+x) (1-2x) + (5+x) (1-3x) = 0
il faut factoriser
(5+x) (1-2x + 1-3x) = 0
(5+x) (-5x + 2) = 0
tu finis - voir A(x) = 0
4x² - 100 = 4 (x-3)²
4x² - 100 = 4 (x² - 6x + 9)
4x² - 100 = 4x² - 24x + 36
24x = 36 + 100
tu peux finir
