15x+225x^2-1-15x/3=8/3 225x^2-1/3=8/3 225x^2-1-8/3=0 225x^2-9/3=0 9(25x^2-1)/3=0 3(25x^2-1)=0 25x^2-1=0 25x^2=1 x^2=1/25 x=1/5