How do you simplify (square root 5 + 9 square root 2)(4 square root 5 - square root 2)?

1 Answer
Jul 27, 2015

Answer:

#=color(blue)(2 +35sqrt(10)#

Explanation:

Expressing the question in numbers:

#=color(blue)((sqrt5+9sqrt2)) * (4sqrt5 - sqrt2)#

Each term within the first bracket needs to be multiplied with each term within the second bracket.

#=color(blue)((sqrt5)) * (4sqrt5 - sqrt2)+color(blue)((9sqrt2)) *(4sqrt5 - sqrt2)#

#=[(sqrt5) (4sqrt5) + (sqrt5)(-sqrt2)]+[9(sqrt2)(4sqrt5) + (9sqrt2)*(-sqrt2)]#

#=[4*5 -sqrt(2*5)] + [36sqrt(2*5) -18]#

#=[20 -sqrt(10)] + [36sqrt10-18]#

Grouping like terms
#=(20-18) -sqrt10+36sqrt10#

#=2 +35sqrt(10)#