Question 408702
x(x+1) = 3(x+x+1)-3
<==> {{{x^2 + x = 3(2x + 1) - 3}}}
<==> {{{x^2 + x = 6x + 3 - 3}}}
<==> {{{x^2 + x = 6x}}}
<==> {{{x^2 -5x = 0}}}
==> x = 0, 5
If x = 0, x +1 = 1 ==> {0,1}
If x = 5, x+1 = 6 ==> {5,6}.