Given expression is x² - 121
This is called Difference of Squared terms, we have a formula that is given as :-
a² - b² = (a - b) · (a + b)
Now using the above formula in the given expression, we get :-
x² - 121
x² - (11)²
here a = x and b = 11
x² - (11)² = (x - 11) · (x + 11)
but it says that student gave the answer as (x - 11) · (x - 11).
So, student's answer should be (x - 11) · (x + 11) instead of product of two (x - 11) terms.
The equation will be of the form:

where A is the amount after t hours, and r is the decay constant.
To find the value of r, we plug the given values into the equation, giving:

Rearranging and taking natural logs of both sides, we get:


The required model is:
You would use the # line to add and subtract from Rose's total. The remaining amount that Rose still owes is $3.
f(x) = x² - 8x + 3
y = x² - 8x + 3
- 3 - 3
y - 3 = x² - 8x + 16
y - 3 + 16 = x² - 8x + 16
y + 13 = x² - 8x + 16
y + 13 = (x - 4)²
- 13 - 13
y = (x - 4)² - 13
f(x) = (x - 4)² - 13