Question

Giải hộ mình bài tìm x nầy với:

a) 7x-x²-6=0

b) 8x³-36x²+57x-27=0

 

Answer 1

a. \(7x-x^2-6=0\)

\(\Rightarrow-x^2+7x-6=0\)

\(\Rightarrow-x^2+x+6x-6=0\)

\(\Rightarrow-x\left(x-1\right)+6\left(x-1\right)=0\)

\(\Rightarrow\left(x-1\right)\left(-x+6\right)=0\)

+) Nếu \(x-1=0\Rightarrow x=1\)

+) Nếu \(-x+6=0\Rightarrow x=6\)

Vậy x=1 hoặc x=6

b. \(8x^3-36x^2+57x-27=0\)

\(\Rightarrow\left(2x\right)^2-3.2^2.x^2.3+3.2x.3^2-3^3=0\)

\(\Rightarrow\left(2x-3\right)^3=0\)

\(\Rightarrow2x-3=0\Rightarrow x=\frac{3}{2}\)

Vậy...........