Tìm x, biết: (a) 2(x−3)−4x=0 (b) x(x+15)+x(x−1)=2x^2+7

a) \(2\left( {x - 3} \right) - 4x = 0\)

\(2x - 6 - 4x = 0\)

\( - 2x = 6\)

\(x =  - 3\)

b) \(x\left( {x + 15} \right) + x\left( {x - 1} \right) = 2{x^2} + 7\)

\({x^2} + 15x + {x^2} - x = 2{x^2} + 7\)

\(14x = 7\)

\(x = \frac{1}{2}\)

c) \(\left( {3x + 2} \right)\left( {2x - 3} \right) - \left( {x - 2} \right)\left( {3x + 5} \right) = 4\)

\((6{x^2} - 5x - 6) - (3{x^2} - x - 10) = 4\)

\(6{x^2} - 5x - 6 - 3{x^2} + x + 10 = 4\)

\(3{x^2} - 4x = 0\)

\(x = 0\) hoặc \(x = \frac{4}{3}\)