Got Homework?
Connect with other students for help. It's a free community.
Here's the question you clicked on:
 0 viewing
Express 7+√5/3+√5 in the form a+b√5 where a and b are intergers
 9 months ago
 9 months ago
Express 7+√5/3+√5 in the form a+b√5 where a and b are intergers
 9 months ago
 9 months ago

This Question is Closed

hartnnBest ResponseYou've already chosen the best response.1
do you know how to rationalize the denominator ?
 9 months ago

hartnnBest ResponseYou've already chosen the best response.1
multiply the numerator and denominator by the conjugate of denominator here, it'll be 3 \(\sqrt5\) what do u get ?
 9 months ago

blackjesus619Best ResponseYou've already chosen the best response.0
What do u get when u multiply it with 7+√5
 9 months ago

hartnnBest ResponseYou've already chosen the best response.1
you mean multiply (1+√5) with (3√5) thats your numerator, you just need to foil to simply it.
 9 months ago

blackjesus619Best ResponseYou've already chosen the best response.0
Its 7√5 in the question can't multiply it with 3√5 that's the part I get confused with
 9 months ago

hartnnBest ResponseYou've already chosen the best response.1
ok, \(7\sqrt 5 \times 3 = 21 \sqrt 5\ \\7\sqrt5\times \sqrt5= 7\sqrt{5^2}=7\times 5=35 \\so \\ 7\sqrt5(3\sqrt5)=21\sqrt535 \) got it ?
 9 months ago

blackjesus619Best ResponseYou've already chosen the best response.0
The answer on my answer sheet is 4√5 how do I get that
 9 months ago

hartnnBest ResponseYou've already chosen the best response.1
ok, then we were supposed to multiply (7+√5) (and not 7√5 as you mentioned "Its 7√5 in the question") then you actually foil : \((7+√5)(3√5)= 7*3 7√5+3√5√5√5 = 21+(7+3)√55\\=164√5=4(4√5)\) and if you simplify the denominator, you'll get a 4 which cancels with the numerator's 4 and you are just left with 4√5
 9 months ago

blackjesus619Best ResponseYou've already chosen the best response.0
I didn't get anything from that sorry but u have confused me a lot
 9 months ago

hartnnBest ResponseYou've already chosen the best response.1
i used this \((a+b)(c+d)=ac+ad+bc+bd\) try to do this with (7+√5)(3√5) take 7 multiply it with 3 and √5 then take √5, multiply it with 3 and √5
 9 months ago

phiBest ResponseYou've already chosen the best response.1
to go over it: \[ \frac{ 7+\sqrt{5}}{3+\sqrt{5}} \] you multiply top and bottom by \( 3 \sqrt{5} \) \[ \frac{ (7+\sqrt{5})( 3 \sqrt{5})}{(3+\sqrt{5})( 3 \sqrt{5})} \]
 9 months ago

phiBest ResponseYou've already chosen the best response.1
now you have two FOIL problems: one on the top and one in the bottom can you do them ? (see hartn's posts on how)
 9 months ago

blackjesus619Best ResponseYou've already chosen the best response.0
I don't know how to do the 7+√5 one
 9 months ago

phiBest ResponseYou've already chosen the best response.1
to do \[ (7+ \sqrt{5})(3 \sqrt{5} ) \] you do 4 multiplies: the First, Outer, Inner, Last This might help http://www.khanacademy.org/math/algebra/polynomials/multiplying_polynomials/v/multiplyingbinomials
 9 months ago
See more questions >>>
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.