bonjour,
1. 25 - ( x+3)² =0
= a²-b² qu'on factorise(a-b)(a+b)
[5-(x+3)][5+(x+3)] =
(5-x-3)(5+x+3) = 0
(-x+2)(x+8) = 0
-x+2 =0
-x =-2
x = 2
x=8 =0
x =-8
2. ( 10-2x)² = 9
(10-2x)²-9 = 0
(10-2x-3)(10-2x+3) = 0
(-2x+7)(-2x+13) = 0
-2x+7 =0
-2x =-7
x =7/2
-2x+13 = 0
-2x =-13
x =13/2
3. 81 = ( -5y + 9)²
81-(-5y+9)² = 0
(9+5y-9)(9-5y+9) = 0
-5y(-5y+18) = 0
-5y = -18
y = 18/5
y = 0
4. (-5x + 6)² = 49
(-5x+6)²-49 = 0
(-5x+6-7)(-5x+6+7) = 0
(-5x-1)(-5x+13) = 0
-5x-1 =0
-5x = 1
x =-1/5
-5x+13 =0
-5x =-13
x =13/5