{ab=96 {a+b=20 {(20-b)b=96 {a=20-b {-b^2+20b-96=0 {a=20-b b^2-20b+96=0 D=400-4*96=400-384=16>0 b1=8 b2=12 {b1=8 {a1=12 {b1=12 {a1=20-12=8