Question

tìm x biết (4x²-25)²-9(2x-5)²=0

Answer 1

\(\Rightarrow\left[\left(2x+5\right)\left(2x-5\right)\right]^2-9\left(2x-5\right)^2=0\)

\(\Rightarrow\left(2x-5\right)^2\left[\left(2x+5\right)^2-3^2\right]=0\)

\(\Rightarrow\left(2x-5\right)^2\left(2x+5-3\right)\left(2x+5+3\right)=0\)

\(\Rightarrow\left(2x-5\right)^2=0\Rightarrow2x-5=0\Rightarrow2x=5\Rightarrow x=\frac{5}{2}\)

hoặc \(2x+2=0\Rightarrow2x=-2\Rightarrow x=-1\)

hoặc \(2x+8=0\Rightarrow2x=-8\Rightarrow x=-4\)

vậy x = 5/2 ; x = -1 ; x = -4