Question

[Bong Bóng Mưa]

a) 5x(12x+7) - 3x(20x-5)= -100

b) 0,6x(x-0,5) - 0,3x(2x+1,3)= 0,138

c) 4x(3x-7) - 6(2x² - 5x + 1) =12

Answer 1

[Lê Trang]

a) 5x(12x + 7) - 3x(20x - 5) = -100

<=> 60x² + 35x - 60x² + 15x = -100

<=> 50x = -100

<=> x = -2

b) 0,6x(x - 0,5) - 0,3x(2x + 1,3) = 0,138

<=> 0,6x² - 0,3x - 0,6x² - 0,39x = 0,138

<=> -0,69x = 0,138

<=> x = -0,2

c) 4x(3x - 7) - 6(2x² - 5x + 1) = 12

<=> 12x² - 28x - 12x² + 30x - 6 = 12

<=> 2x - 6 = 12

<=> 2x = 18

<=> x = 9