4 * ( X - 10) = 4X - 40
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общий знаменатель Х * ( Х + 20 )
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( Х + 20) * ( 4Х - 40 ) - Х * ( 4Х - 40) = X^2 + 20X
4X^2 - 40X + 80X - 800 - 4X^2 + 40X = X^2 + 20X
80X - 800 - X^2 - 20X = 0
-X^2 + 60X - 800 = 0
D = 3600 - 4*(-1)*(-800) = 400
V D = 20
X1 = ( - 60 + 20 ) : ( - 2 ) = 20
X2 = ( - 80 ) : ( - 2 ) = 40
Ответ 20 и 40