How can I solve this equation involving two variables?

[Aladin]

please help me in solving this question.
3x^2+xy-y^2=81 ; x+y=7


I will be thankful to you

 

[D H]

We don't do your homework here. Show some work, please.

 

[Dark Fire]

Also it's not a question:
"Hey"
-Hey
"3x^2+xy-y^2=81 ; x+y=7 ??"
-Yes
"OK."

 

[tiny-tim]

please help me in solving this question.
3x^2+xy-y^2=81 ; x+y=7


I will be thankful to you

Hi Aladin!

Hint: do the easy equation first.

So x = … ?

 

[symbolipoint]

Find y in terms of x and substitute...

 

[shamrock5585]

this isn't even precalculus its basic algebra

 

[Aladin]

it is not my home work I am just trying to solve it because I am learning basic math.so please help me in solving this equation

 

[konthelion]

Just follow everyone's advice and solve find x in terms of y or vice versa y in terms of x and substitute back into your equation.

 

[shamrock5585]

after you solve in terms of the other with one equation you have to plug in for the other equation