Question

tim x biết 

a) 2x(x-5)-2x²=20

b)5x(2x-7)+2x(8-5x)=5

c) 4x(7x-5)-7x(4x-2)= -12

Answer 1

a) 2x(x - 5) - 2x² = 2x² - 10x - 2x² = -10x = 20 => x = 20 : (-10) = -2

b) 5x(2x - 7) + 2x(8 - 5x) = 10x² - 35x + 16x - 10x² = -19x = 5 => x = \(\frac{5}{-19}=\frac{-5}{19}\)

c) 4x(7x - 5) - 7x(4x - 2) = 28x² - 20x - 28x² + 14x = -6x = -12 => x = -12 : (-6) = 2

Answer 2

MK mới học lớp 7 thôi nhưng mk làm vài câu nha

a) 2x(x-5)-2x²=20

    2x²-100x-2x²=20

    100x=20

     x=20:100

      x=\(\frac{1}{5}\)

Answer 3

a) Ta có : 2x ( x - 5 ) - 2x² = 20

=> 2x ( x - 5 ) - 2x.x = 20

=> 2 x ( x - 5 - x ) = 20

=> 2x . ( -5 ) = 20

=> -10 x = 20

=> x = -2

Chọn mik mik làm tiếp

Answer 4

a, \(2x\times\left(x-5\right)-2x^2=20\)

\(\Rightarrow2x^2-10x-2x^2=20\Rightarrow-10x=20\)

\(\Rightarrow x=20\div\left(-10\right)=\left(-2\right)\)

b, \(5x\times\left(2x-7\right)+2x\times\left(8-5x\right)=5\)

\(\Rightarrow10x^2-35x+16x-10x^2=5\) \(\Rightarrow-19x=5\)

\(\Rightarrow x=\frac{-5}{19}\)

c, \(4x\times\left(7x-5\right)-7x\times\left(4x-2\right)=-12\)

\(\Rightarrow28x^2-20x-28x^2+14x=-12\)  \(\Rightarrow-20x+14x=-12\)

\(\Rightarrow-6x=-12\) \(\Rightarrow x=\left(-12\right)\div\left(-6\right)=2\)