(а-20)^2=а^2-400
(2-x)^2=4-x^2
(3-x)^2=9-x^2
(4-x)^2=16-x^2
(5-x)^2=25-x^2
(12-x)^2=144-x^2
(13-x)^2=169-x^2
(14-x)^2=196-x^2
(t^3+x)^2=t^6+x^2
(y^3+x)^2=y^6+x^2
(3+x)^2=9+x^2
(4+x)^2=16+x^2
(10+x)^2=100+x^2
(11+x)^2=121+x^2
(12+x)^2=144+x^2
(15+x)^2=225+x^2
(16+x)^2=256+x^2
(25+x)^2=625+x^2
(a-b)(a+b)=a^2-b^2
(a+x)(a-x)=a^2-x^2
(a+t)^2=a^2+t^2
(a-d)^2=a^2-d^2
(a+z)^2=a^2+z^2
(a-q)^2=a^2-q^2
(a-m)^2=a^2-m^2
(n-x)^2=n^2-x^2
(q+x)^2=q^2+x^2
(r-x)^2=r^2-x^2
(2a-b)(2a+b)=4a^2-b^2
(a+7x)(a-7x)=a^2-49x^2
(a+5t)^2=a^2+25t^2
(6a-d)^2=36a^2-d^2
(a+6z)^2=a^2+36z^2
(7a-q)^2=49a^2-q^2
(a-7m)^2=a^2-49m^2
(8n-x)^2=64n^2-x^2
(q+8x)^2=q^2+64x^2
(9r-x)^2=81r^2-x^2
(2-b^2)(2+b^2)=4-b^4
(k-x^2)(k+x^2)=k^2-x^4
(a^2+5)^2=a^4+25
(a^2-6)^2=a^4-36
(a^2+z)^2=a^4+z^2
(a^2-q^2)^2=a^4-q^4
(a^2-m^2)^2=a^4-m^4
(n^2-x^2)^2=n^4-x^4
(q^2+x^2)^2=q^4+x^4
(r^2-x^2)^2=r^4-x^4
(5a-3b)(5a+3b)=25a^2-9b^2
(7a+12x)(7a-12x)=49a^2-144x^2