-4 as a fraction

Please help quick, or if - 4 can't be a fraction let me know.
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Which of the following statements is true? a. the irrational number system is not closed under multiplication, because the product of two irrational numbers is always a rational number. b. the irrational number system is not closed under multiplication, because the product of two irrational numbers is not always an irrational number. c. the irrational number system is closed under multiplication, because the product of two irrational numbers is always an irrational number. d. the irrational number system is closed under multiplication, because the product of two irrational numbers is always a rational numbers. reset submit

Im so bad at fractions they are not my best math thing to work on

For the right triangle shown, the lengths of two sides are given. find the third side. leave your answer in simplified, radical form.