Cho 2x = a + b + c. Chứng minh rằng: (x-a)(x-b) + (x-b)(x-c) + (x-c)(x-a) = ab + bc + ca - x^2
Giải thích
VT=x−ax−b+x−bx−c+x−cx−a
=ab+bc+ca+3x2−2xa+b+c
=ab+bc+ca+3x2−2x.2x
=ab+bc+ca−x2=VP
VT=x−ax−b+x−bx−c+x−cx−a
=ab+bc+ca+3x2−2xa+b+c
=ab+bc+ca+3x2−2x.2x
=ab+bc+ca−x2=VP