Question

Tìm x, biết:

a)2x(x-5)-x(3+2x)=26

b)6x²-11x+3=0

Answer 1

a, \(2x\left(x-5\right)-x\left(3+2x\right)=26\)
⇔ \(2x^2-10x-3x-2x^2=26\)
⇔\(-13x=26\)
⇔\(x=-2\)

b, \(6x^2-11x+3=0\)
\(x_1=\dfrac{3}{2}\)
\(x_2=\dfrac{1}{3}\)

Answer 2

a.

\(2x\left(x-5\right)-x\left(3+2x\right)=26\)

\(\Leftrightarrow\) \(2x^2-10x-3x-2x^2=26\)

\(\Leftrightarrow\) \(-13x=26\)

\(\Leftrightarrow\) \(x=-2\)

b.

\(6x^2-11x+3=0\)

\(\Delta=b^2-4ac\)

\(=\left(11\right)^2-4.6.3\)

\(=49>0\)

\(\Rightarrow\) phương trình có 2 nghiệm phân biệt

\(x_1=\dfrac{-b+\sqrt{\Delta}}{2a}=\dfrac{11+7}{2.6}=\dfrac{3}{2}\)

\(x_2=\dfrac{-b-\sqrt{\Delta}}{2a}=\dfrac{-11-7}{2.6}=\dfrac{1}{3}\)