1.
x = 7-y
2(7-y)-3y = 4
14-2y-3y = 4
-5y = -10
y = 2
x = 7-y = 7-2 = 5
2.
y = -2x+6
x -4 -2 0 2 4
y 14 10 6 2 -2
3.
(2a-5)(2a+5)-4(a-3)² =
= 4a²-25 -4(a²-6a+9) =
= 4a²-25 -4a²+24a-36 =
= 24a -61
