Question

Решите уравнение: (7x + 1)(x - 3) + 20(х - 1)(x + 1) = 3(3x - 2)^2 + 13

Answer 1

$(7x+1)(x-3)+20(x-1)(x+1)=3(3x-2)^{2}+13\\ 7x^{2} -21x+x-3+20(x^{2} -1)=3(9x^{2} -12x+4)+13\\7x^{2} -20x-3+20x^{2}-20=27x^{2} -36x+12+13\\27x^{2} -20x-23=27x^{2} -36x+25\\16x=48\\x=3$