Question

a,x(x+1)(x+6)-x^3=5x b,(3x-5)(7-5x)+(5x+2)(3x-2)-2=0 c, 2(x-3)+7(2-x)+11

 

Answer 1

a: \(x\left(x+1\right)\left(x+6\right)-x^3=5x\)

=>\(x\cdot\left(x^2+7x+6\right)-x^3-5x=0\)

=>\(x^3+7x^2+6x-x^3-5x=0\)

=>\(7x^2+x=0\)

=>x(7x+1)=0

=>\(\left[{}\begin{matrix}x=0\\7x+1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-\dfrac{1}{7}\end{matrix}\right.\)

b: \(\left(3x-5\right)\left(-5x+7\right)+\left(5x+2\right)\left(3x-2\right)-2=0\)

=>\(-15x^2+21x+25x-35+15x^2-10x+6x-4-2=0\)

=>42x-41=0

=>42x=41

=>\(x=\dfrac{41}{42}\)