(у²+5)(у²-5)=(у²)²-5²=у⁴-25
(20р+0,3q)(20p-0,3q)=400p²-0,09q²
(3b+7a⁴)(3b-7a⁴)=9b²-49a^8
33*27=(30+3)(30-3)=30²-3²=900-9=891
49*51=(50-1)(50+1)=50²-1²=2500-1=2499
(4m-10n)(4m+10n)-(4m-n)²=
=16m²-100n²-(16m²-8mn+n²)=
= 16m²-100n²-16m²+8mn-n²=8mn-101n²
(4x+3y)²=16x²+24xy+9y²
(m-2n)²=m²-2mn+4n²