How many times?

How many times do 2x and x2+1 intersect and what r the points of intersection? I will tell reason for this question later :)

20 Answers

11
Anirudh Narayanan ·

What was you?

1
RAY ·

are yaar...koi baat nahi.......x2 wale graph ko y axis pe higher kar do by 1.......n plot it..u will get the points........u can find the third point by plotting the graph dude...on a big paper..just try i guess u can plot it.....just shift mah x2 grph above by +1 on y axis..n u will get x2+1.

11
Anirudh Narayanan ·

How will find out third point?

P.S
Graph shd b between 2x and x2+1

1
RAY ·

thin graph is 2x............even i wwas quite shocked wen i plotted the graphs n found that there are 3 points....one is in -ve side.......anoder is 2[that was easy....2x and x2] are both 22 here............and the third intersection is between x=4 and 8 sumwhere......just try plotting till 5 .u will understand...........

1
RAY ·

1
RAY ·

will post in 5 mins..

1
RAY ·

u guess 1 root hoga......

11
Anirudh Narayanan ·

Tho sahi wala kya hai?

1
RAY ·

sorry sorry!!mera graph galat tha.......

11
Anirudh Narayanan ·

Where's the third point of intersection?

1
varun ·

I think 3..., x=0 and x=1.. the other one i will try later :P

The slopes show that they must meet 3 times...

33
Abhishek Priyam ·

That was me :P

11
Anirudh Narayanan ·

In a test I took here, i got this question and gave the ans as two (u can't expect me to draw the graph to scale!!) as 0 and 1 were the only solutions I could think of. Well, thanks everybody :))

1
Prashant Shekhar ·

Applying numerical technique (which you guys will learn in IIT), the third root comes out to be 4.2575

11
Anirudh Narayanan ·

Any other way to get the ans?

1
varun ·

Slope of x2+1 = 2x.

Slope of 2x = 2xloge2.

At x=1, slope of x2+1 > 2x.... so x2 + 1 is steeper and on the inside.

so seeing the values of 2xloge2 > 2x for higher numbers then they must meet at another point.

I think the another point is around x=4.5

11
Anirudh Narayanan ·

I still dont get it :(

33
Abhishek Priyam ·

By slope he means check slope of slope of both curves at x=1
and limit of slope of 2x-(x2+1) as x→+∞

You will understand.
[1]

11
Anirudh Narayanan ·

what do u mean "The slopes show that they must meet 3 times" ?

1
Rohan Ghosh ·

yes , at three points

x=0
x=1 and the other point cannot be calculated exactly

Your Answer

Close [X]