Subtraction of two real numbers may be defined of what operation

Tiara buys the pizza shown below: a circular pizza is shown. the edge of one slice is marked ab. what does the curve ab represent?

When are triangles considered similar? a. corresponding angles are equal andcorresponding sides are proportionalb. corresponding angles are proportional andcorresponding sides are equalc. corresponding angles are equal orcorresponding sides are proportionald. corresponding angles are proportional orcorresponding sides are equal select the best answer from the choices providedmark this and retumsave and exitnext

Can someone factor this fully? my friend and i have two different answers and i would like to know if either of them is right. you in advance. a^2 - b^2 + 25 + 10a