Question

is (5+√5) (5-√5) a rational number or an irrational number (explain)​

Answer 1

Answer:

Step-by-step explanation:

(5 + √5)(5 - √5) = 5^2 - (√5)^2

                          = 25 - 5

                          = 20

Therefore, the number is rational.

Answer 2

Answer:

It is a rational number

Step-by-step explanation:

According to following identity

$a {}^{2} - b {}^{2} = (a + b)(a - b)$

$(5 + \sqrt{5} )(5 - \sqrt{5})$

can be written as

${5}^{2} - { \sqrt{5} }^{2}$

which is equal to 25-5=20 which is a rational number.

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