Réponse:
Exercice 64:
A= 3(x + 5)²
A= 3(x + 5) (x + 5)
A= 3(x×x + x×5 + 5×x + 5×5)
A= 3 (x²+5x+5x+25)
A= 3 (x²+10x+25)
A= 3x²+30x+75
B= 2(10-3y)²
= 2(10-3y) (10-3y)
= 2(10×10 + 10×(-3y) -3y×10 -3y×(-3y))
= 2(100 -30y -30y +9y²)
= 2 ( 100 - 60y +9y²)
= 200-120y +18y²
C= 5(9y-4) (9y+4)
= 5((9y)²-4²)
= 5(81y²-16)
= 5×81y² + 5×(-16)
= 405y² -80
Exercice 65:
I= 2(6y-5)² -12+10y
= 2(6y-5) (6y-5) -12 +10y
= 2 (36y²-30y-30y+25) -12+10y
= 2 ( 36y²-60y+25) -12+10y
= 2 ( 36y²-50y+13)
= 72y²-100y+26
J= (1+9x)(1-9x) + (3x +7)²
= 1²-(9x)² + (3x+7) (3x+7)
= 1 - 81x² + 9x²+21x +21x +49
= -72x² + 42x + 50
K= 6x²-18-(x-4)²
= 6x²-18-(x-4) (x-4)
= 6x²-18-(x²-4x-4x+16)
= 6x²-18-(x²-8x+16)
= 6x²-18-x²+8x-16
= 5x²+8x-34
Exercice 66:
1.
AB² = ( 3 x + 1)² - (3 x) ²
AB² = ( 3 x + 1 - 3 x) ( 3 x + 1 + 3 x)
AB² = 6 x + 1
2. formule aire du carré: c×c
la longueur d'un côté:AB= 6x +1
donc c×c= (6x+1)²
