Đáp án:
`(a + b + c)^2 + (a - b + c)^2 - 4b^2`
`= [(a + c )+ b]^2 + [(a + c) - b]^2 - 4b^2`
`= (a + c)^2 + 2(a + c)b + b^2 + (a + c)^2 - 2(a + c)b + b^2 - 4b^2`
`= 2(a + c)^2 + 2b^2 - 4b^2`
`= 2(a + c)^2 - 2b^2`
`= 2[(a + c)^2 - b^2]`
`= 2(a + c - b)(a + c + b)`
b, `a(b^2 - c^2) - b(c^2 - a^2) + c(a^2 - b^2)`
`= a(b^2 - c^2) - bc^2 + ba^2 + ca^2 - cb^2`
`= a(b - c)(b + c) - (bc^2 + cb^2) + (ba^2 + ca^2)`
`= a(b - c)(b + c) - bc(c + b) + a^2(b + c)`
`= (b + c)[a(b - c) - bc + a^2]`
`= (b + c)(ab - ac - bc + a^2)`
`= (b + c)[(ab + a^2) - (ac + bc)]`
`= (b + c)[a(b + a) - c(a + b)]`
`= (b + c)(a + b)(a - c)`
Giải thích các bước giải:
