Question 54429
X*Y=86 & 2X+2Y=40 THUS 2X=40-2Y OR X=20-Y THEN SUBSTITUTE (20-Y) FOR X IN THE FIRST EQUATION WE GET (20-Y)Y=86 OR 20Y-Y^2-86=0 OR -Y^2+20Y-86=0 OR
Y^2-20Y+86=0 USING THE QUADRATIC EQUATION (-B+/-SQRT(B^2-4AC))/2A WE GET ANSWERS OF:

-10+/-SQRT14 OR 13.7442 & 6.258