1) What is the equivalent of this?
-5x(2x+7y)+7xy-4x(y+3)
just expand, then collect like terms
= -10x^2 - 35xy + 7xy - 4xy - 12x
= -10x^2 -32xy - 12x
or
= -2(5x^2 + 16xy + 6x)
-5x(2x+7y)+7xy-4x(y+3)
= -10x^2 - 35xy + 7xy - 4xy - 12x
= -10x^2 -32xy - 12x
or
= -2(5x^2 + 16xy + 6x)