Question

tìm x 
a)  2x(x-1)-2x²=7
b)  x(x-2)+3x-6=0
c)  (x²-9)+(x+5)(x-3)=0

Answer 1

\(a,2x\left(x-1\right)-2x^2=7\\ =>2x^2-2x-2x^2-7=0\\ =>-2x-7=0\\ =>x=-\dfrac{7}{2}\\ b,x\left(x-2\right)+3x-6=0\\ =>x\left(x-2\right)+3\left(x-2\right)=0\\ =>\left(x+3\right)\left(x-2\right)=0\\ =>\left[{}\begin{matrix}x-2=0\\x+3=0\end{matrix}\right.=>\left[{}\begin{matrix}x=2\\x=-3\end{matrix}\right.\\ c,\left(x^2-9\right)+\left(x+5\right)\left(x-3\right)=0\\ =>\left(x-3\right)\left(x+3\right)+\left(x+5\right)\left(x-3\right)=0\\ =>\left(x-3\right)\left(x+3+x+5\right)=0\\ =>\left[{}\begin{matrix}x-3=0\\2x+8=0\end{matrix}\right.=>\left[{}\begin{matrix}x=3\\x=-4\end{matrix}\right.\)