Question

Уравнение: x+y=13 2x-y=17 и доказать,что 3(a-2)в квад-(a-1)(a+2)-2(a-1)(a+1)=16-13a ( !

Answer 1

1.
{х+у=13
{2х-у=17
________
3х=30
х=10

10+у=13
у=3

ответ: (10;3)

2.
${3(a - 2)}^{2} - (a - 1)(a + 2) - \\ - 2(a - 1)(a + 1) = 16 - 13a \\ 3(a - 2)(a - 2) - ( {a}^{2} + a - 2) - \\ - 2( {a}^{2} - 1) = 16 - 13a \\ 3( {a}^{2} - 4a + 4) - {a}^{2} - a + 2 - \\ - 2 {a}^{2} + 2 = 16 - 13a \\ 3 {a}^{2} - 12a + 12 - {a}^{2} - a + 2 - \\ - 2 {a}^{2} + 2 = 16 - 13a \\16 - 13a = 16 - 13a$