Find the number of roots satisfying 3 x − x 2 + x − 2 = 0 .
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
Make the graphs of y = 3 x and y = x 2 − x + 2 and check for the number of intersections.
But in exam hall? What to do there bro? No point in plotting graph.
Log in to reply
Nope. Plotting the graphs of these functions is no big deal, these type of problems can't be even done without graphs.
So there's no way you can find x without graphs ?
@Chew-Seong Cheong please tell me the answer of this question. and the solution too.
@Calvin Lin Please help me do this sum . Dont delete it.
Problem Loading...
Note Loading...
Set Loading...
According to the question : 3 x = x 2 − x + 2
The R.H.S. of the equation i.e. x 2 − x + 2 has minimum value is 4 7 which is at x = 1 / 2
At x = 1 / 2 the L.H.S. of the equation 3 x has value 1 . 7 3 2 which is lower than 7 / 4 .So, at x = 1 / 2 3 x is lower than x 2 − x + 2 .
Taking the difference of their rate of increasing (i.e. derivative) 3 x l n 3 − ( 2 x − 1 )
It is easily seen that 3 x l n 3 − ( 2 x − 1 ) > 0
At x = 1 / 2 3 x has alower value than x 2 − x + 2 .But rate of increasing show that 3 x increase faster than x − x + 2 .
So, they must intersect at exactly one point and then increases.
So, there exists one solution.