Question

a rational number subtracted by a rational number equals?
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Answer 1

You still get a rational number.

The sum/subtraction between rational numbers is defined as follows:

$\dfrac{a}{b}\pm\dfrac{c}{d} = \dfrac{ad\pm bc}{bd}$

The expression $ad\pm bc$ is the sum/difference between the products of integers, and so is still an integer. This means that

$\dfrac{ad\pm bc}{bd}$

is still a ratio between integers, and thus a rational.