algebra
posted by Jenny .
Two questions actually. Please only respond with stepbystep answers. Feel free to change the numbers, I just need to know how to do it...
1.) Factor Completely:
4a^2 + 81  36a
2.) In a right triangle, find the length of the side not given. b= 2 c= sqrt. 13

1.) 4a^2 36a + 81
What are factors of 81? (3 * 3 * 3 * 3)
What are factors of 4? (2 * 2)
What combination of these factors (or the whole number) can give you 36 for the middle term?
2.) Pythagorean theorem
a^2 + b^2 = c^2
a^2 + 4 = 13
Can you work it from here?