Part A:
For this case we have the following polynomial:

First we make a common factor a^2:
We have then:

From here, we can factor the quadratic expression into parentheses.
We have then:
Answer:
Part B:
For this case we have the following polynomial:

We factor the expression.
To do this, we write two numbers that added are 14 and multiplied are 49.
We have then:
Answer:
Part C:
For this case we have the following polynomial:

We observe that we have a binomial, therefore, we must factor.
To do this, we write two numbers that added are 0 and multiplied are -100.
We have then:
Answer:
