Someone !
add and simplify to find the answer for #15 and #12.
provide answers are both not sure if number 12 is correct and explain why! ?

see explanation

Step-by-step explanation:

12

Since the denominators are like, add the numerators leaving the denominator

=

=

15

We require the denominators to be like before we can add.

factor x² - 4 as a difference of squares

x² - 4 = (x + 2)(x - 2)

Expressing as

+

multiply the numerator/denominator of the first fraction by (x - 2)

= +

Expand and simplify the numerators, leaving the denominator

=

=

answer: -8.2562234e+13

problem:

f(x) = - 2/3x + 5; f(5/2)

substitute 5/2 in for x:

f(5/2) = -2/3(5/2) + 5

simplify the right side:

f(5/2) = -5/3 + 5

f(5/2) = 10/3

f(5/2) = 10/3

i hope this !