`#kehuydiet`
1/ `(a-b+c)^2-2(a-b+c)(c-b)+(b-c)^2`
`= (a-b+c)^2-2(a-b+c)(c-b)+(c-b)^2`
`= (a-b+c-c+b)^2`
`= a^2`
2/ `(2x-5)(4x^2+10x+25)(2x+5)(4x^2-10x+25)-64x^4`
`= (8x^3-125)(8x^3+125)-64x^4`
`= 64x^6-15625-64x^4`
3/ `(a+b)^3+(a-b)^3-2a^3`
`= a^3+3a^2b+3ab^2+b^3+a^3-3a^2b+3ab^2-b^3-2a^3`
`= 6ab^2`