Question

Tìm x:

\(\left(x+3\right)\left(x-3\right)-\left(x-5\right)^2=20\)

Answer 1

\(\Leftrightarrow x^2-9-\left(x^2-10x+25\right)=20\)

\(\Leftrightarrow10x-34=20\)

\(\Leftrightarrow10x=54\)

\(\Leftrightarrow x=\frac{27}{5}\)

Answer 2

(x+3)(x-3)-(x-5)²=20

<=>x²-9-x²+10x-25=20

<=>10x=54

=>x=27/5

=> n pt là :{27/5}