# Answer to Question #10121 in Linear Algebra for Mehwish

Question #10121

the value of personal computer is decreasing linearly over time.Two points indicate its price at two different times:

after one year Price=Rs.45000.

after two year Price=Rs.40.000

(1)Determine a linear equation representing this information.

(2)Predict when the computer will be worthless.

after one year Price=Rs.45000.

after two year Price=Rs.40.000

(1)Determine a linear equation representing this information.

(2)Predict when the computer will be worthless.

Expert's answer

Let's construct a line crossing points (1;45000) and (2,40000):

(t-1)/(2-1) = (P-45000)/(40000-45000);

t-1 = 9-P/5000;

P = 5000(10-t).

Here P is price and t is time (in years).

(2)Predict when the computer will be worthless.

The computer will be worthless when price will be equal to zero:

5000(10-t) = 0 ==> t = 10.

So, the computer will be worthless after 10 years.

(t-1)/(2-1) = (P-45000)/(40000-45000);

t-1 = 9-P/5000;

P = 5000(10-t).

Here P is price and t is time (in years).

(2)Predict when the computer will be worthless.

The computer will be worthless when price will be equal to zero:

5000(10-t) = 0 ==> t = 10.

So, the computer will be worthless after 10 years.

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