Question

下列计算正确的是

1. A.
   5y²·4yx²＝9x³y³
2. B.
   (-2x³yⁿz)(-4xⁿ⁺¹yⁿ-3)＝8xⁿ⁺⁴y²n-3
3. C.
   (-x^n-2y²)(-xy^m)²＝-xⁿy²m+2
4. D.
   (-7a²b³)(5ab²c)＝-2a²b⁶c

Answer 1

C

A项5y²·4yx²＝20x²y³；

B项(-2x³yⁿz)(-4xⁿ⁺¹yⁿ-3)＝8xⁿ⁺⁴y²n-3z；

C项(-x^n-2y²)(-xy^m)²＝(-x^n-2y²)·(x²y²m)＝-xⁿy²m+2；

D项(-7a²b³)(5ab²c)＝-35a³b⁵c．