On the highway, a car can travel 21 miles per gallon of gas. If the car travels for 4 hours on the highway at a rate of 65 miles
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Given:
Expression is
To prove:
If r is any rational number, then is rational.
Step-by-step explanation:
Property 1: Every integer is a rational number. It is Theorem 4.3.1.
Property 2: The sum of any two rational numbers is rational. It is Theorem 4.3.2.
Property 3: The product of any two rational numbers is rational. It is Exercise 15 in Section 4.3.
Let r be any rational number.
We have,
It can be written as
Now,
3, -2 and 4 are rational numbers by property 1.
is rational by Property 3.
are rational by Property 3.
is rational by property 2.
So, is rational.
Hence proved.