А) 3х(2х-1)-6х(7+х)=90 б)1,5x(3+2x)=3x(x+1)-30 в)5x(12x-7)-4x(15x--11)=30+29x г)24х-6х(13х-9)=-13-13х(6х-1) объясните подробно

Ответ:

alina130410

17.06.2020 09:04

$a)\\3x(2x-1)-6x(7+x)=90\\6x^2-3x-42x-6x^2=90\\-45x=90\\x=\frac{90}{-45}\\x=-2\\\\\\b)\\1,5x(3+2x)=3x(x+1)-30\\4,5x+3x^2=3x^2+3x-30\\3x^2-3x^2+4,5x-3x=-30\\1,5x=-30\\x=\frac{-30}{1,5}\\x=-20\\\\B)\\5x(12x-7)-4x(15x-11)=30+29x\\60x^2-35x-60x^2+44x=30+29x\\9x-29x=30\\-20x=30\\x=\frac{30}{-20}\\x=-1,5\\\\ r)\\24x-6x(13x-9)=-13-13x(6x-1)\\24x-78x^2+54x=-13-78x^2+13x\\24x-78x^2+78x^2+54x-13x=-13\\65x=-13\\x=\frac{-13}{65}\\x=\frac{-1}{5}\\x=-0,2$

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Ответ:

СофаСтар2

17.06.2020 09:04

$1) \ 3x(2x-1)-6x(7+x)=90\\\\ \underline{6x^2} - 3x - 42x- \underline{6x^2} = 90\\\\ -3x - 42x = 90\\\\ -45x = 90 \ | : -45\\\\ \boxed{x = -2}\\\\$

$2) \ 1.5x(3 + 2x) = 3x(x + 1) - 30\\\\ 4.5x + \underline{3x^2} = \underline{3x^2} + 3x - 30\\\\ 4.5x = 3x - 30 \ | - 3x\\\\ 4.5x - 3x = -30\\\\ 1.5x = -30 \ | : 1.5\\\\ \boxed{x = -20}$

$3) \ 5x(12x-7)-4x(15x-11)=30+29x\\\\ \underline{60x^2} - 35x - \underline{60x^2} + 44x = 30 + 29x\\\\ - 35x + 44x = 30 + 29x \ | - 29x\\\\ -35x + 44x - 29x = 30\\\\ -20x = 30 \ | : -20\\\\ \boxed{x = -1.5}$

$4) \ 24x-6x(13x-9)=-13-13x(6x-1)\\\\ 24x - \underline{78x^2} + 54x = -13 - \underline{78x^2} + 13x\\\\ 24x + 54x = -13 + 13x \ | - 13x\\\\ 24x + 54x - 13x = -13\\\\ 65x = -13 \ | : 65\\\\ \boxed{x = -\frac{13}{65} = -\frac{1}{5} = -0.2}$