Unformatted text preview: they are 300
miles apart. So, we have a right triangle here. That means that we can use the Pythagorean Theorem to say, ( 25t ) + ( 20 ( t  2 ) )
2 2 = ( 300 ) 2 This is a quadratic equation, but it is going to need some fairly heavy simplification before we
can solve it so let’s do that. 625t 2 + ( 20t  40 ) = 90000
2 625t 2 + 400t 2  1600t + 1600 = 90000
1025t 2  1600t  88400 = 0
© 2007 Paul Dawkins 108 http://tutorial.math.lamar.edu/terms.aspx College Algebra Now, the coefficients here are quite large, but that is just something that will happen fairly often
with these problems so don’t worry about that. Using the quadratic formula (and simplifying that
answer) gives, 1600 ± 365000000 1600 ± 1000 365 32 ± 20 365
=
=
2050
2050
41 t= Again, we have two solutions and we’re going to need to determine which one is the correct one,
so let’s convert them to decimals. t= 32 + 20 365
= 10.09998
41 and t= 32  20 365
= 8.539011
41 As with the previous example the negative answer just doesn’t make any sense. So, it looks like
the car A traveled for 10.09998...
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This note was uploaded on 06/06/2012 for the course ICT 4 taught by Professor Mrvinh during the Spring '12 term at Hanoi University of Technology.
 Spring '12
 MrVinh

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