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x2 - x = 20
x2 - x - 20 = 0
(x + 4)(x - 5) = 0
x + 4 = 0 or x - 5 = 0
x = -4 or x = 5
x2 - x = 20 x2 - x - 20 = 0 (x - 5)(x + 4) = 0 x - 5 = 0 and x + 4 = 0 So, x = 5 ans x = -4
x: x2 - 81 = 0
Divide both sides of the equation by x: x2 = 9x x2 / x = 9x / x x = 9
x - x2 - 9x + 14 = 0 ; whence, x2 + 8x = 14 , x2 + 8x + 16 = 30 , and x + 4 = ±√30 . Therefore, x = ±√30 - 4 .
x2 + 20x +0 =30 [(20/2)2 =100] x2 + 20x + 100 =30 +100 √(x+10)2=√130 x+10=√130 x= −10+√130 √ means square root