Solve the two simulatneous equations x^2+y^2=18 and x-y=3

             1) X2 +2Y2= 18 2) X - Y = 3   Rearrange 2) in the form X=3-Y then substitute in to 1); (3-y)2 +2Y2=18, this is your new equation 3 9+3Y+3Y+Y2+2Y2=18 3) 9+6y+3Y2= 18 Divide equation 3) by 3 3 +2Y+Y2=6 Solve for Y by equating to zero then factorising in to double brackets; Y2+2Y -3 = 0 (Y+3)(Y-1)=0 when (Y-1)=0, Y =1 and when (Y+3)=0, Y=-3 solve x by substituting your found Y values in to equation 2 when Y=1; X-1 = 3 so X=4 When Y=-3; X--3=3, so X=0