What is the representation of the third element in an array called a?

In factoring by grouping, what would you have for step 3 for the following? step 1: x^3 +5x^2 +4x+20 step 2: x^2 (x+5)+4(x+5) step 3: ?

Which best explains why this triangle is or is not a right triangle?

The vet charges $45 for an office visit and $10 for each vaccination your dog needs. write an eaquation