Question

Tìm x

A) 2x(x-5)-x(2x+3)=25

B) (3y^2-y+1)(y-1)+y^2(4-3y)=5/2

C) 2x^2 +3( x-1)( x+1)= 5x(×+1)

Answer 1

a, \(2x\left(x-5\right)-x\left(2x+3\right)=25\)

\(\Rightarrow2x^2-10x-2x^2-3x=25\)

\(\Rightarrow-13x=25\Rightarrow x=\dfrac{-25}{13}\)

b, \(\left(3y^2-y+1\right)\left(y-1\right)+y^2\left(4-3y\right)=\dfrac{5}{2}\)

\(\Rightarrow3y^3-y^2+y-3y^2+y-1+4y^2-3y^3=\dfrac{5}{2}\)

\(\Rightarrow2y-1=\dfrac{5}{2}\Rightarrow2y=\dfrac{7}{2}\Rightarrow y=\dfrac{7}{4}\)

c, \(2x^2+3\left(x-1\right)\left(x+1\right)=5x\left(x+1\right)\)

\(\Rightarrow2x^2+3\left(x^2+x-x-1\right)=5x^2+5x\)

\(\Rightarrow2x^2+3x^2-3=5x^2+5x\)

\(\Rightarrow-5x=3\Rightarrow x=\dfrac{-3}{5}\)