1)3x^2+4xy-4x(x+y)=3x^2+4xy-4x^2v-4x=-x^2
2)(c-1)(4+c)=4c+c^2-4-c=3c+c^2-4=3c+x^2-4=x^2+3x-4
3)(3x-y)(5y+2x) =15xy+6x^2-5y^2-2xy=13xy+6x^2-5y^2
4)30p+25p^2=5p×(6+5p)
5)2(m+3)-m(m+3)=(2-m)(m+3)
6)5-x/4 - 4-x/5 =1
5(5-x)-4(4-x)=20
25-5x-16+4x=20
9-x=20
-x=20-9
-x=11
x=-11