Which of the following is a monomial?

The degree of $4x{y}^2{z}^{3}4xy^2z^3$

The degree of $3x^2-5+7x^3-6x^{5}3x^2\; -\; 5\; +\; 7x^3\; -\; 6x^5$

If $A=5x^2+3xy+2y^2,B=-2y^2-3xy+4x^{2}A\; =\; 5x^2\; +\; 3xy\; +\; 2y^2,\; B\; =\; -2y^2\; -\; 3xy\; +\; 4x^2$  then A + B = ______

Which of the following is a group of like terms?

5x $\times \backslash times$ (-3y) =

The product of 5x, 6y and 7z

$(a+b{)}^2-(a-b{)}^2=(a\; +\; b)^2\; -\; (a\; -\; b)^2\; =$

The formula involved in the product of $302\times 298302\backslash times298$

$(3m-2n^2)\times (-7mn)=(3m\; -\; 2n^2)\; \backslash times\; (-7mn)\; =$ ____