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1. Im having trouble doing this.
It says leave answer in surd form
2x+3y=13
x^2+y^2=78

i rearranged the first to equal

x=(13-3y)/2

then substitute it into the second

((13-3y)/2)^2+y^2=78

then expand it all which i got
13y^2-78y-143=0

then i dont know what to do
2. Have you learnt the quadratic formula yet?
That's what you have to use to solve the equation.
3. Notice that 13 divides 13, 78 and 143, so divide through by 13; then use the quadratic formula.

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