Упростите позя 2a(a-3)-(a-6)(a+3) (b-2)^2-5b(b-1) 4xy+2(x-y)^2

Решите задачу:

$2a(a - 3) - (a - 6)(a + 3) = \\ = 2 {a}^{2} - 6a - ( {a}^{2} + 3a - 6a - 18) = \\ = 2 {a}^{2} - 6a - {a}^{2} + 3a + 18 = \\ = {a}^{2} - 3a + 18$

${(b - 2)}^{2} - 5b(b - 1) = \\ = {b}^{2} - 4b + 4 - 5 {b}^{2} + 5b = \\ = - 4 {b}^{2} + b + 4$

$4xy + 2 {(x - y)}^{2} = \\ = 4xy + 2( {x}^{2} - 2xy + {y}^{2} ) = \\ = 4xy + 2 {x}^{2} - 4xy + 2 {y}^{2} = \\ = 2 {x}^{2} + 2 {y}^{2} = 2( {x }^{2} + {y}^{2} )$