Question

tìm x,biết :

a) 3x( x-8 )+16=2x

b)(5-x)^2=25

Answer 1

Zaza, tự làm nữa đi a~.

a) \(3x\left(x-8\right)+16=2x\)

\(\Rightarrow3x^2-24x+16=2x\)

\(\Rightarrow3x^2-26x+16=0\)

\(\Rightarrow\left(3x^2-24x\right)-\left(2x-16\right)=0\)

\(\Rightarrow3x\left(x-8\right)-2\left(x-8\right)=0\)

\(\Rightarrow\left(x-8\right)\left(3x-2\right)=0\)

Để đẳng thức xảy ra \(\Rightarrow\left[\begin{array}{nghiempt}x-8=0\\3x-2=0\end{array}\right.\)\(\Rightarrow x\in\left\{8;\frac{2}{3}\right\}\)

b) \(\left(5-x\right)^2=25=5^2=\left(-5\right)^2\)

\(\Rightarrow5-x\in\left\{\pm5\right\}\Rightarrow x\in\left\{0;10\right\}\)