I struggle with simultaneous equations, when you have a quadratic involved

Example solve the following, equation 1: x²+2y=9 equation 2: y=x+3In this example we have to use substitution, therefore we sub in equation 2 into 1 to get the following x²+2(x+3)=9 , now we must expand the brackets which will give us x²+2x+6=9. REMEMBER with quadratics we always want the equation to =0, therefore we minus 9 from both sides to give us our equation, x²+2x-3=0. This is the equation we must factorise!-the numbers must multiply to make -3-and sum to 2Build your brackets (x-3)(x+1)=0 so x = 3 or -1, now substitute back into equation 2 and you will get y=3+3 and y=-1+3 giving the values that y= 6 or 2. FINISHED!