x(x+1) + (x+1)(x+2) = 98
(x+1)(x + x+2) = 98
(x+1)(2x+2) = 98
(x+1) · (2(x+1)) = 98
2·(x+1)(x+1) = 98
2·(x+1)² = 98 | :2
(x+1)² = 49
○ x+1 = 7 => x = 7-1 => x = 6
○ x+1 = -7 => x = -7-1 = -8
