Week15-Applications of Rational Equations

This week we learned how to solve the unknown value from the score formula

For example:


Then we make all the term time common denominator

so we get the common denominator is 4v




Then we learn how to solve the unknow number in the life things

This is the one of the example
we get Mary’s apprentice need 9 hours long to build a deck than it takes Marcy

So we make Mary need x hours to finish , her apprentice need x+9 hours to finish

And if they do together , so they will finish in 20 hours

so we know after 1 hour Mary finished\frac{1}{x} , her apprentice finished \frac{ 1 }{x+9}

so we got a function that are after 20 hours

\frac{20}{x}+\frac{20}{x+9}=1(this ‘1’ is mean 20 over 20)

And you use the way that times common denominator

we got x^2 -31x-180=0

then we factor

we get (x-36)(x+5)=0

And we get 36 ,-5

but -5 is not belong to the question

so we just get 36 is mary

than we get 36+9=45 is her apprentice

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