Turn on thread page Beta
    • Thread Starter
    Offline

    10
    ReputationRep:
    Simplify fully (√𝑎 + √4𝑏)(√𝑎 − 2√𝑏)
    • Community Assistant
    Offline

    20
    ReputationRep:
    Community Assistant
    (Original post by error405)
    Simplify fully (√𝑎 + √4𝑏)(√𝑎 − 2√𝑏)
    So simplify
    • Community Assistant
    • Study Helper
    Offline

    20
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by error405)
    Simplify fully (√𝑎 + √4𝑏)(√𝑎 − 2√𝑏)
    First look at \sqrt{4b}. How can you simplify / write it in a different way?
    • Community Assistant
    • Study Helper
    Offline

    20
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by error405)
    ...
    Hi, please don't create duplicate threads - I have removed the thread you just created. If you still need help, please post all your working that you have tried.
    • Thread Starter
    Offline

    10
    ReputationRep:
    (Original post by Notnek)
    Hi, please don't create duplicate threads - I have removed the thread you just created. If you still need help, please post all your working that you have tried.
    sorry couldn't find the thread

    √4B=2b right??
    • Community Assistant
    • Study Helper
    Offline

    20
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by error405)
    sorry couldn't find the thread

    √4B=2b right??
    Just checking sincce your original question isn't clear. Do you mean

    (\sqrt{a} +\sqrt{4} \ {b})(\sqrt{a}-2\sqrt{b})

    or

    (\sqrt{a} +\sqrt{4b})(\sqrt{a}-2\sqrt{b})

    I assumed it was the second one...
    • Thread Starter
    Offline

    10
    ReputationRep:
    my working out:

    a+2√ab+2b√a-4b√b
    Offline

    17
    ReputationRep:
    (Original post by Notnek)
    First look at \sqrt{4b}. How can you simplify / write it in a different way?
    Multiply the brackets out to begin with
    Posted on the TSR App. Download from Apple or Google Play
    • Thread Starter
    Offline

    10
    ReputationRep:
    (Original post by Notnek)
    Just checking sincce your original question isn't clear. Do you mean

    (\sqrt{a} +\sqrt{4} \ {b})(\sqrt{a}-2\sqrt{b})

    or

    (\sqrt{a} +\sqrt{4b})(\sqrt{a}-2\sqrt{b})

    I assumed it was the second one...

    yes the 2nd one
    Offline

    17
    ReputationRep:
    (Original post by error405)
    sorry couldn't find the thread

    √4B=2b right??
    No. 2b would be square root 4b^2
    Posted on the TSR App. Download from Apple or Google Play
    • Community Assistant
    • Study Helper
    Offline

    20
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by error405)
    yes the 2nd one
    Okay so \sqrt{4b} = \sqrt{4}\times \sqrt{b} = 2\sqrt{b}

    It then becomes

    (\sqrt{a} +2\sqrt{b})(\sqrt{a}-2\sqrt{b})

    Can you now try multiplying out the brackets? Post all your working if you get stuck.
    • Community Assistant
    • Study Helper
    Offline

    20
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by 12ksmith)
    Multiply the brackets out to begin with
    I recommended simplifying that term before expanding because then you have something of the form (x+y)(x-y) and it's easier to expand.
    Offline

    17
    ReputationRep:
    (Original post by Notnek)
    I recommended simplifying that term before expanding because then you have something of the form (x+y)(x-y) and it's easier to expand.

    Well yeah, you could simplify the left bracket to where root 4b becomes 2 root b. I guess that could make it a little simpler. But you would have to multiply out anyways.

    Personally I would find this easier to multiply out first then simplify from there.
    Posted on the TSR App. Download from Apple or Google Play
    • Thread Starter
    Offline

    10
    ReputationRep:
    (Original post by Notnek)
    Okay so \sqrt{4b} = \sqrt{4}\times \sqrt{b} = 2\sqrt{b}

    It then becomes

    (\sqrt{a} +2\sqrt{b})(\sqrt{a}-2\sqrt{b})

    Can you now try multiplying out the brackets? Post all your working if you get stuck.
    a-2√ab+2√ab-4√ b
    • Thread Starter
    Offline

    10
    ReputationRep:
    (Original post by error405)
    a-2√b-2√ab+2√ab-4√ b
    a-4√ b
    • Thread Starter
    Offline

    10
    ReputationRep:
    Thank you
    • Community Assistant
    • Study Helper
    Offline

    20
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by error405)
    a-4√ b
    Nearly but 2\sqrt{b}\times 2\sqrt{b} does not give 4\sqrt{b}. Have another go at this.

    Also please try to use brackets more in your posts e.g. instead of √ab, write √(ab) because √ab looks like \sqrt{a} \ b, which is not what you mean.
    • Thread Starter
    Offline

    10
    ReputationRep:
    (Original post by Notnek)
    Nearly but 2\sqrt{b}\times 2\sqrt{b} does not give 4\sqrt{b}. Have another go at this.

    Also please try to use brackets more in your posts e.g. instead of √ab, write √(ab) because √ab looks like \sqrt{a} \ b, which is not what you mean.
    is it (4b) ?
    • Community Assistant
    • Study Helper
    Offline

    20
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by error405)
    is it (4b) ?
    Correct
    • Thread Starter
    Offline

    10
    ReputationRep:
    a - (4b)
 
 
 
Poll
Do you think parents should charge rent?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.