Question

(5x-7)(x+3) = 5x² +5x

Answer 1

$(5x - 7)(x + 3) = {5x}^{2} + 5x \\ {5x}^{2} + 15x - 7x - 21 = {5x}^{2} + 5x \\ 15x - 7x - 21 = 5x \\ - 21 = - 3x \\ x = 7$