I don’t know I suck at math sadly
The most simple form (I'm defining the parabola to be an upwards-opening one) would be
Answer: x-intercept 13,0 y 0, 
Step-by-step explanation:
This problem is mainly concerned with setting up an equation.
let's add the interest rates times their respective investment amounts:



simplify:

sum of interest:

1780 = (9000+x) 0.10 + x 0.06 + (11000-2x)0.08


solution:
He does not have any invested in the 6%, while he has 9000 invested at 10% and 11,000 invested at 8%
to check:


So this ended up being a trick problem because he does not actually have any invested in the 6% option.
To decompose a fraction to one whole, there are different methods to use. The fraction can be decomposed either by division, multiplication(if there are more than one fraction), or addition(if there are more than one fractions).
Example:
Given 8/2, decompose by division:
To do this, divide the numerator by denominator