Factor the expression

9x^2-16

(3x-4) (3x+4)

Step-by-step explanation:

9x^2-16

9x^2  is a product of squares = (3x)^2

16 is a product of squares  = 4^2

so

9x^2-16  is the difference of squares

(a^2 - b^2) = (a-b) (a+b)   where a = 3x and b =4

9x^2-16  = (3x-4) (3x+4)

step-by-step explanation:

infinity is the answer

11) obtuse

13)right

15) acute