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
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