3√21 means how many and why?
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Answer:
Explanation:
You know that for real, positive numbers you have
√
a
⋅
√
b
=
√
a
⋅
b
This means that you can write
√
3
⋅
√
21
=
√
3
⋅
21
If you write
21
as the product of its prime factors
3
and
7
, you can say that
√
3
⋅
21
=
√
3
⋅
3
⋅
7
=
√
9
⋅
7
Now use the same multiplication property of radicals to write
√
9
⋅
7
=
√
9
⋅
√
7
=
3
⋅
√
7
=
3
√
7
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