1 a+[a+b+c]-[b-a]=3a+c
2 a×{b+c}-a[b-c]=2ac
3 {[a÷b]×{b÷a+1]}×{b÷a}=1
4 a+b-{c×2a}-ac+3[ab+ac}=a+b+3ab
5 {a+b+c}²+1=a²+b²+c²+2ab+2ac+2bc+1
6 {a+b}{a-b}+2a{3b-2b]=a²+b²-2ab