`a)x^2(x+4)(x-4)-(x^2+1)(x^2-1)`
`=x^2(x^2-16)-(x^2+1)(x^2-1)`
`=x^4-16x^2-(x^4-1)`
`=-16x^2+1`
`b) (a-b+c)^2-(a-c)^2-2ac+2ab`
`=a^2+b^2+c^2-2ab-2bc+2ac-(a^2-2ac+c^2)-2ac+2ab`
`=a^2+b^2+c^2-2ab-2bc+2ac-a^2+2ac-c^2-2ac+2ab`
`=b^2-2bc+2ac`
a) Ta có: \(x^2\left(x+4\right)\left(x-4\right)-\left(x^2+1\right)\left(x^2-1\right)\)
\(=x^2\left(x^2-16\right)-\left(x^4-1\right)\)
\(=x^4-16x^2-x^4+1\)
\(=-16x^2+1\)
b) Ta có: \(\left(a-b+c\right)^2-\left(a-c\right)^2-2ac+2ab\)
\(=\left(a-b+b-a+c\right)\left(a-b+c+a-c\right)-2ac+2ab\)
\(=c\left(2a-b\right)-2ac+2ab\)
\(=2ac-2bc-2ac+2ab\)
\(=2ab-2bc\)
