Question

simplify (√21+√5)(√21-√5)​

Answer 1

Step-by-step explanation:

Explanation: √21=√3⋅7 has no square factors that can be 'moved outside the square root sign'. So √21 cannot be simplified. It cannot be expressed as a rational number (fraction), so the best we can do with normal notation is to either stick with √21 or give an approximation, such as √21≈4.58 .

Answer 2

(√21+√5)(√21-√5)

it is in the form of

(a+b)(a-b)=a²-b²

=(√21)²-(√5)²

=21-5

=16

hope it helps you

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