Chứng minh đẳng thức sau: (x-y)(x^4 + x^3y + x^2y^2 + xy^3 + y^4) = x^5 - y^5
Giải thích
VT=x−yx4+x3y+x2y2+xy3+y4
=x5+x4y+x3y2+x2y3+xy4−x4y−x3y2−x2y3−xy4−y5
=x5−y5+x4y−x4y+x3y2−x3y2+x2y3−x2y3+xy4−xy4
=x5−y5=VP
VT=x−yx4+x3y+x2y2+xy3+y4
=x5+x4y+x3y2+x2y3+xy4−x4y−x3y2−x2y3−xy4−y5
=x5−y5+x4y−x4y+x3y2−x3y2+x2y3−x2y3+xy4−xy4
=x5−y5=VP