3(1)2X (2)XY (3)0.5M (4)4A
4(1)(2X+3)(2X-3) (2)X(X-4)
5(1)y(x+2)(x-2) (2) (4+a)(4-a) (3)25(m^2+2mn+n^2)-36(m^2-2mn+n^2)=122mn-11m^2-11n^2=-11(m+n)^2
6(729+271)(729-271)=1000*458=458000
4 (1) [x+(2y-3)]*[x-(2y-3)]=x^2-4y^2+12y-9
(2)a^2+b^2+c^2-2ac+2bc-2ab
(3)m^2+n^2=(m+n)^2-2mn=100-48=52
(m-n)^2=m^2+n^2-2mn=(m+n)^2-4mn=100-96=4