(a+5)(b+5)
=ab+5a+5b+25
（3x-y)(2x+3y)
=6x²+7xy-3y²
(3x-2)(2x-3)(x+2)
=(6x²-13x+6)(x+2)
=12x³-13x²+6x+12x²-26x+12
=12x³-x²-20x+12
(四分之三xy²）²
=16分之9x²y^4
(2ab²）x（-3a)
=-6a²b²