Giải giúp tôi cần gấp

`a) A = 16xy^8 . 2x^2 . 3y^7`

`A = ( 16 . 2 . 3 )( x . x^2 )( y^8 . y^7 )`

`A = 96x^3y^15`

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`b) B = 2x^5 - x^3 - 1/2x^5 + 3x^4 + x^3 - 8x^4 + 25`

`B = ( 2x^5 - 1/2x^5 ) + ( -x^3 + x^3 ) + ( 3x^4 - 8x^4 ) + 25`

`B = 3/2x^5 - 5x^4 + 25`

`-------`

`a^n . a^m = a^(n + m)`