The Student Room Group

Simple C1 Co-ordinate Geometry Question - Help!

I'm using the distance formula, I'm confused where the square root of 1+4 came from. Can someone help?
(edited 7 years ago)
mm.PNG5.6KB
Reply 1
Avatar for Tom__
Tom__
2
post the question
Reply 2
Avatar for Jessinoch
Jessinoch
OP
9
Original post by Tom__
post the question


Its part (iii)
question.PNG24.7KB
Original post by Jessinoch
I'm using the distance formula, I'm confused where the square root of 1+4 came from. Can someone help?


Did the question specify what form the answer should be in?
If you know where the sqrt49/4 + 49 comes from, the entire thing has just been divided by 12.25 (or 49/4)
Original post by Fractite
If you know where the sqrt49/4 + 49 comes from, the entire thing has just been divided by 12.25 (or 49/4)


But how do you get 7/2 on the outside of the square root?
Reply 6
Avatar for Tom__
Tom__
2
are you sure you did the previous parts of the question correctly? I got a different answer to you
Original post by Speedbird129
But how do you get 7/2 on the outside of the square root?


The square root of 12.25 is 3.5, so you use that I think.
Surely it would be easier to just do square root of 49/4 + 49 and add them to get square root 61.25. This therefore equals 7 square root 5 divided by 2 which is the same answer??
Reply 9
Avatar for Jessinoch
Jessinoch
OP
9
Original post by Tom__
are you sure you did the previous parts of the question correctly? I got a different answer to you


Yeah, this is from physicsandmathstutor.com
Reply 10
Avatar for Jessinoch
Jessinoch
OP
9
Original post by Speedbird129
Surely it would be easier to just do square root of 49/4 + 49 and add them to get square root 61.25. This therefore equals 7 square root 5 divided by 2 which is the same answer??


Yeah but this is C1 so you can't use a calculator
Reply 11
Avatar for Jessinoch
Jessinoch
OP
9
Original post by Speedbird129
Did the question specify what form the answer should be in?

it said in surd form
Reply 12
Avatar for B_9710
B_9710
18
All they've done is simplify. 494+49≡494(1+4)≡(494)121+4 \displaystyle \sqrt{\frac{49}{4}+49}\equiv \sqrt{\frac{49}{4}\left (1+4 \right )}\equiv \left (\frac{49}{4} \right )^{\frac{1}{2}}\sqrt{1+4} .
So going one step further the answer is 725 \displaystyle \frac{7}{2} \sqrt{5} .
Original post by Jessinoch
I'm using the distance formula, I'm confused where the square root of 1+4 came from. Can someone help?


I assume you know how you get to 494+49\sqrt{\frac{49}{4}+49} at which point you know you can factor a 49 out of the expression under the square roots so you get 49(14+1)\sqrt{49(\frac{1}{4}+1)} and then you can also factor out a quarter which gets you 49⋅14⋅(1+4)\sqrt{49\cdot \frac{1}{4}\cdot (1+4)} and then it's just the matter of splitting it into two square roots, one of which square roots nicely into a fraction.

494⋅1+4\sqrt{\frac{49}{4}} \cdot \sqrt{1+4}
Reply 14
Avatar for Jessinoch
Jessinoch
OP
9
Original post by B_9710
All they've done is simplify. 494+49≡494(1+4)≡(494)121+4 \displaystyle \sqrt{\frac{49}{4}+49}\equiv \sqrt{\frac{49}{4}\left (1+4 \right )}\equiv \left (\frac{49}{4} \right )^{\frac{1}{2}}\sqrt{1+4} .
So going one step further the answer is 725 \displaystyle \frac{7}{2} \sqrt{5} .


Thankyou!
Reply 15
Avatar for Jessinoch
Jessinoch
OP
9
Original post by RDKGames
I assume you know how you get to 494+49\sqrt{\frac{49}{4}+49} at which point you know you can factor a 49 out of the expression under the square roots so you get 49(14+1)\sqrt{49(\frac{1}{4}+1)} and then you can also factor out a quarter which gets you 49⋅14⋅(1+4)\sqrt{49\cdot \frac{1}{4}\cdot (1+4)} and then it's just the matter of splitting it into two square roots, one of which square roots nicely into a fraction.

494⋅1+4\sqrt{\frac{49}{4}} \cdot \sqrt{1+4}


Thankyou!

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you