The teacher will be very surprised to see your correct solution 😉
-28*x2 + 8*x21 + 14*x23 + 14*x1*x3 + 16*x1*x2 + 32*x2*x3 = 0
16*x1*x2 + 14*x1*x3 + 32*x2*x3 - 28*x2 + 8*x21 + 14*x23 = 0