How do you evaluate # 5\sqrt { 7} + 2\sqrt { 28} - 4\sqrt { 63}#?

Question

1524 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2017-07-22T07:46:31

#-3sqrt7#

#5sqrt7+2sqrt28-4sqrt63#

We begin by reducing the numbers in the square root signs by first factorising and then removing the squares.

#5sqrt7+2sqrt(7xx2xx2)-4sqrt(7xx3xx3)#

From the second and third square root signs, we can remove #2# and #3# respectively and multiply them with the number before the square root sign.

#5sqrt7+(2xx2)sqrt7-(4xx3)sqrt7#

#5sqrt7+4sqrt7-12sqrt7#

Keeping the #sqrt7# constant, add and subtract the whole numbers.

#(5+4-12)sqrt7#

#-3sqrt7#