It’s 6 because it’s challenging to figure it out but it’s six I just got the correct answer
I think it is c but pet me know

We are to find the value of

First we need to find the inverse of f(x) . The inverse of

is

.
Steps to find inverse of f(x) are shown below in the image.
So

=
Therefore, the correct answer is option C
Answer:
15
Problem:
Given that a*b = 2ab - 3b. Determine 2*(3*5)
Step-by-step explanation:
First we find 3*5 using rule a*b = 2ab - 3b.
3*5=2(3)(5)-3(5)
3*5=30-15
3*5=15
Now we are left with 2*15 in which we will still use the rule a*b=2ab-3b.
2*15=2(2)(15)-3(15)
2*15=60-45
2*15=15
Therefore, 2*(3*5)=15.
Since there are only 4 terms in the sum, it's not too much work to expand it as

Alternatively, we can use the well-known formulas


These sums start at n = 0, so in our given sum we will keep track of the 0-th term separately:

as expected.