Please help I am in dire need.

Which math sentence can be used to determine if the triangle is a right triangle?

Plz determine whether the polynomial is a difference of squares and if it is, factor it. y2 – 196 is a difference of squares: (y + 14)2 is a difference of squares: (y – 14)2 is a difference of squares: (y + 14)(y – 14) is not a difference of squares

Given the two similar triangles, how do i find the missing length? if a=4, b=5, and b'=7.5 find a'