jabarkan dan sederhanakanlah

a)(x.x)(x.6)(4.x)(4.6)=x²+6x+4x+24=x²+10x+24.
b)(a².a²)(a².2b)(-b.a²)(-b.2b)=a pangkat 4+2a²b-a²b-2b²=a pangkat 4-2b².
c)(3m.3m)(3m.-2n)(2n.3m)(2n.-2n)=9m²-6mn+6mn-4n²=9m²-4n².
d)(9x.2x)(9x.-7y)(4y.2x)(4y.-7y)=18x²-63xy+8xy-28y²=18x²-55xy-28y².