Please help and explain. I am very confused and frustrated.

Select the correct answer from the drop-down menu. subtracting 3xy^2 from 8xy^2 gives the same result as the expression. [tex]3xy ^{2} - 8xy ^{2} [/tex][tex] { - 7xy}^{2} - {2xy}^{2} [/tex][tex] {7xy}^{2} - {2xy}^{2} [/tex]

Which of the following is true for the relation f(x)=2x^2+1

If a 36 inch yardstick casts a 21 foot shadow, how tall is a building whose shadow is 168 feet? what is the scale factor