A computer is bought for $1380 and sold 10 months later for $520. Assuming the function is linear, find the depreciation formula and the value of the computer after 4 months.

Question

jim_thompson5910 · Answer

What's the change in price?

anonymous · Answer

860?

jim_thompson5910 · Answer

over how many months?

anonymous · Answer

4

jim_thompson5910 · Answer

no, read the problem over again

anonymous · Answer

10? or 6?

jim_thompson5910 · Answer

"A computer is bought for $1380 and sold 10 months later for $520"

jim_thompson5910 · Answer

so the computer drops by $860 in 10 months

Slope = rise/run = -860/10 = -86

jim_thompson5910 · Answer

the slope of -86 means the price is dropping by $86 each month

anonymous · Answer

so is the rise 1380?

jim_thompson5910 · Answer

"rise" is the change in price

jim_thompson5910 · Answer

change in price = 1380 - 520 = 860

jim_thompson5910 · Answer

the change is negative because we have a price drop

jim_thompson5910 · Answer

so I guess you should say 520 - 1380 = -860

anonymous · Answer

so - 860 is after 4 months?

anonymous · Answer

doesent make sense whats the equation to solve?

jim_thompson5910 · Answer

do you see how I'm getting the slope?

jim_thompson5910 · Answer

the slope just represents the change in price per month

anonymous · Answer

yea by subtracting 86 dollors each month

jim_thompson5910 · Answer

if the price drops by 860 in 10 months

then the price drops by 86 each month

jim_thompson5910 · Answer

correct

jim_thompson5910 · Answer

now let's say that at time x = 0 months, the price is $1380

this is the y-intercept because x = 0 here

anonymous · Answer

so is the answer 86 after four months?

jim_thompson5910 · Answer

so b = 1380

jim_thompson5910 · Answer

slope: m = -86
y-intercept: b = 1380

jim_thompson5910 · Answer

y = mx+b

y = -86x+b

y = -86x+1380

jim_thompson5910 · Answer

Plug in x = 10 into y = -86x+1380 and tell me what you get

anonymous · Answer

ok

anonymous · Answer

520

jim_thompson5910 · Answer

so that equation confirms that in 10 months, the price is $520

jim_thompson5910 · Answer

if you were to plug in x = 4, you'd get your answer

anonymous · Answer

yep

anonymous · Answer

ok

anonymous · Answer

1036?

jim_thompson5910 · Answer

correct

anonymous · Answer

ok and the depreciation formula is

jim_thompson5910 · Answer

you just used the depreciation formula to calculate the price at 4 months

anonymous · Answer

y= -86x+1380?

jim_thompson5910 · Answer

correct

anonymous · Answer

ok

jim_thompson5910 · Answer

-86 tells you how much the price is dropping per month
1380 is the starting price

anonymous · Answer

ok makes sense

jim_thompson5910 · Answer

I'm glad it's clicking

anonymous · Answer

yea its better this stuff seems hard though

anonymous · Answer

not very easy to figure out

jim_thompson5910 · Answer

but now it should be a bit easier

anonymous · Answer

yes