<span>2-4x+5y=0
1. Выражаем x
-4x=-5y-2
x=(5y-2)/-4
</span>2. Выражаем y
5y=4x-2
y=(4x-2)/5
(5а+3)+(-2а²+а+7) = 5а+3-2а²+а+7 = -2а²+6а+10
(х+6у)+(3-6у) = х+6у+3-6у = х+3
х²-3ху+у²-(х²-у²) = х²-3ху+у²-х²+у² =2у²-3ху
(a-b+c)+(a-c)-(a-b-c) = a-b+c+a-c-a+b+c = a+с
(7х²-5х+3)-(7х²-5) = 7х²-5х+3-7х²+5 = -5х+8
2/5х + 5/6 = 1/6 - 7/25х
10/25х + 7/25х = 1/6 - 5/6
17/25х = - 2/3
Х = - 2/3 : 17/25
Х = - 50/51
ответ будет ровно =========== 512