manny’s pizza shows declining sales over the last few months. their net profit in hundreds of dollars follows the arithmetic sequence 4, 1, −2, −5, …, −56. what is their total profit over this time period?

The total profit over this period is -546

Step-by-step explanation:

Given

Sequence: 4, 1, −2, −5, …, −56

Required

Determine the total profit

To do this, we simply calculate the sum of terms (Sn)

But first, we need to determine the value of n using

Where:

Substitute these values in the above formula, we have:

Collect Like Terms

Recall that:

This gives:

The total profit over this period is -546

we have three similar triangles, because each has a right angle and shares an angle.   let's write the angles in order: opposite to short leg, long leg, hypotenuse.

cab similar to bad similar to cbd

or as ratios,

ca: ab: cb = ba: ad: bd = cb: bd: cd

we also know

ac = ad + cd

(ad+cd): ab: cb = ba: ad: bd = cb: bd: cd

(ad+cd)/cb=cb/cd

we have cb=6, ad=5 and seek x=cd.

we reject the negative root and conclude x=4

answer: 4