X2+y2=18.X-2y=-3

Solution for X2+y2=18.X-2y=-3 equation:

X2+X2=18.X-2X=-3

We move all terms to the left:

X2+X2-(18.X-2X)=0

We add all the numbers together, and all the variables

X2+X2-(+16X)=0

We add all the numbers together, and all the variables

2X^2-(+16X)=0

We get rid of parentheses

2X^2-16X=0

a = 2; b = -16; c = 0;
Δ = b2-4ac
Δ = -162-4·2·0
Δ = 256
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{256}=16$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-16)-16}{2*2}=\frac{0}{4}
=0
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-16)+16}{2*2}=\frac{32}{4}
=8
$