X^2 + 7X = 0X(X + 7) = 0X = 0 or X = -7
49X^2 - 9 = 049X^2 = 9X^2 = 9/49X = ±3/7
X^2 + 25 = 0X^2 = -25No real solutions
15 - 2У = 8У^2 + 3X(У + 5)8У^2 - 3XУ - 2У + 3X*5 - 15 = 08У^2 - (3X + 2)У - 15 = 0
3(X^2 + 5) = 4X^2 + X(1 - X)3X^2 + 15 = 4X^2 + X - X^23X^2 + 15 = 3X^2 + X
-2X^2 + 6 = 3(X^2 + X + 2)-2X^2 + 6 = 3X^2 + 3X + 6
X^2 + 7X = 0
X(X + 7) = 0
X = 0 or X = -7
49X^2 - 9 = 0
49X^2 = 9
X^2 = 9/49
X = ±3/7
X^2 + 25 = 0
X^2 = -25
No real solutions
15 - 2У = 8У^2 + 3X(У + 5)
8У^2 - 3XУ - 2У + 3X*5 - 15 = 0
8У^2 - (3X + 2)У - 15 = 0
3(X^2 + 5) = 4X^2 + X(1 - X)
3X^2 + 15 = 4X^2 + X - X^2
3X^2 + 15 = 3X^2 + X
-2X^2 + 6 = 3(X^2 + X + 2)
-2X^2 + 6 = 3X^2 + 3X + 6