Question

Please help me . Fast
25 th problem

Answer 1

$a(1 - a) + 2(a - 3) + 5(3 - 1) = 0 \\ = a - {a}^{2} + 2a - 6 + 10 = 0 \\ = - {a}^{2} + 3a + 4 = 0 \\ = {a}^{2} - 3a - 4 = 0 \\ = {a}^{2} - 4a + a - 4 = 0 \\ = a(a - 4) + 1(a - 4) \\ (a + 1)(a - 4) \\ a = - 1 \\ a = 4$