Quadratic Equation- finding the root quadratic using factorization

D= 81(a+b)^2- 36(2a²+5ab+2b^2 )

   ^{= -9 a^2- 9b^2-18ab}

^{therefore, x= [9(a+b)+ 3(a+b)] / 18 and [9(a+b)- 3(a+b)]/ 18}

 ^{x=2(a+b)/3 and (a+b)/3}