How do you simplify -7\sqrt { 21} \cdot \sqrt { 28}?
1 Answer
Apr 13, 2017
Explanation:
When adding or subtracting radicals, they have to be the same.
When mutliplying however, the rule does not apply.
So for
Thus,
-7xx(sqrt7*sqrt3)xx(sqrt7*sqrt4)
Group like terms to make simplification easier
-7xxsqrt7xxsqrt7xxsqrt4xxsqrt3
Note,
sqrt7xxsqrt7=7
How???
(color(red)sqrt7)^(color(red)2)=7
So we have,
-7xx7xxsqrt4xxsqrt3
We know that,
sqrt4=2
Leaving us with
-7xx7xx2xxsqrt3
-49xx2xxsqrt3
-98*sqrt3
Thus, our answer is
rArr-98sqrt3