(-5,2) concave up
Hope this helps :)
N is the variable, you solve by subtracting 6 from 20, getting n = 14.
Are you missing something?
2xy=7
5xy=9
does not have a solution.
If you mean
2x+y=7
5x+y=9
please say so.
Answer:

Step-by-step explanation:
Given

Required
Find the equivalent
We start by changing the / to *


Factorize 10a - 5

Expand 4a² - 1


Express (2a)² - 1² as a difference of two squares
Difference of two squares is such that: 
The expression becomes

Combine both fractions to form a single fraction

Divide the numerator and denominator by 2a - 1

Simplify the numerator


Hence,
= 