Solve simultaneously: x^2+y^2=25 and y-3x=13

The substitution method means we have to rearrange the linear equation to find a variable, either x or y, then substitute it into the quadratic (and more difficult to solve) equation, as follows...x²+y²=25 y=3x+13x²+(3x+13)²=25x²+9x²+78x+169=2510x²+78x+144=05x²+39x+72Factorise...(5x+24)(x+3)=0x=-24/5, x=-3Sub in linear equation for y...when x=-24/5, y=-7/5when x=-3, y=4