Question 916663

x − 2y = 3
y2 − x2 = 3x + 9
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Use ^ (Shift 6) for exponents.
I'll assume you mean 
x − 2y = 3
y^2 − x^2 = 3x + 9
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x − 2y = 3 --> x = 2y + 3
Sub for x in the other eqn
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y^2 − x^2 = 3x + 9
y^2 − (2y+3)^2 = 3(2y+3) + 9
Now it's 1 equation in y.
Can you do the rest?  for help, or to check your work email me via the TY note.