^ - значок возведения в степень
2x + 7y = 1
2^(x + y) = 4^(x - y + 2)
2x + 7y = 1
2^(x + y) = (2^2)^(x - y + 2)
2x + 7y = 1
2^(x + y) = 2^(2x - 2y + 4)
2x + 7y = 1
x + y = 2x - 2y + 4
2x + 7y = 1
2x - x - 2y - y + 4 = 0
2x + 7y = 1
x - 3y + 4 = 0
x = 3y - 4
2 * (3y - 4) + 7y = 1
x = 3y - 4
6y - 8 + 7y = 1
x = 3y - 4
13y = 1 + 8
x = 3y - 4
13y = 9
x = 3y - 4
y = 9/13
x = 3 * (9/13) - 4
y = 9/13
x = 27/13 - 4
y = 9/13
x = 27/13 - 52/13
y = 9/13
x = -25/13
y = 9/13
2 * (-25/13) + 7 * 9/13 = 1
-50/13 + 63/13 = 1
13/13 = 1
1 = 1