[tex]a)\\(x+1)(x-2)+(x+2)(x-1)=x^2-2x+x-2+x^2-x+2x-2=2x^2 - 4\\\\b)\\(5k+n)(k-2n)-k(4k+n)=5k^2-10kn+nk-2n^2-4k^2-kn=k^2 - 10kn - 2n^2\\\\c)\\(4y+3)(y-2)-2y(4-2y)=4y^2-8y+3y-6-8y+4y^2=8y^2 - 13y - 6\\\\d)\\-(3c-2)(c-1)-c(c-2)=-3c^2+3c+2c-2-c^2+2c=- 4c^2 + 7c - 2\\\\e)\\2(3a^2-1)-(a+2)(a+2)=6a^2-2-a^2-2a-2a-4=5a^2 - 4a - 6\\\\f)\\5x^2(x^2+1)-(x^2-2)(x^2+3)=5x^4+5x^2-x^4-3x^2+2x^2+6=4x^4 + 4x^2 + 6[/tex]
