Question

\(\left(5x+1\right)^2-\left(5x+3\right)\left(5x-3\right)=30\)

Answer 1

Ta có:  (5x+1)^2 - (25x^2 - 9)= 30

             (5x+1 - 5x)(5x+1+5x) + 9 = 30

                  10x +10 = 30 

=>  x=2