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#