5x^2+7x=0 X^2-10=39 2)x^2=81

Question

5x^2+7x=0
X^2-10=39
2)x^2=81

Answer 1

5x^2+7x=0
x ( 5x + 7) = 0
x = 0  i  5x + 7 = 0
             5x = - 7
             x = - 7/5            

X^2-10=39
x^2 = 39 + 10
x^2 = 49
x^2 - 49 = 0
x^2 - 7^2 = 0
(x+7)(x-7) = 0
x + 7 = 0    i  x - 7 = 0
x = - 7        i  x = 7

2)x^2=81
x^2 = 81 = 0
x^2 - 9^2 = 0
(x+9)(x-9) = 0
x + 9 = 0  i  x - 9 = 0
x = - 9      i  x = 9
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