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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