onto

a function f:R→R

f(x)=(px2 +6x-8)/(p+6x-8x2)

Find the integral values of p for which the given function is onto .

9 Answers

62
Lokesh Verma ·

I will give u a hint..

Think in tems of the neighborhood of the roots of numerator and denominator!

(Good question.. took me sometime to think! :)

1
Indraneel Chatterjee ·

is it 2 to 14?

1
Indraneel Chatterjee ·

you can eqaute it to y and then y should be frm -∞ to ∞.

using quadraic equations property and determinants. ull get 2 to 14.

is there any other method.

62
Lokesh Verma ·

Sorry dude for the late reply..

More Hint: (btw this is an interesting question to solve without using differentiation as u said :)

See this figure..

U need to take these cases...
And try them ..

I am sure u will get the answer using these..

there will be many cases.. u will have to eliminate some!

I hope this helps?

1
Indraneel Chatterjee ·

yes this helps

1
Indraneel Chatterjee ·

but the graph of the lower polynomial should not touch the x axis because if it does the denominator fr some value of x will be 0 so the function will be undefined . graph should lie below the x axis . please explain a litlle more in detail.

62
Lokesh Verma ·

Denominator unfortunately has to be zero (otherwise this will not be satisfied.)!

Basically u are correct.. but i think this question requires us to overlook that aspect.

Using these graphs... and limits and continuity.. we can get the necessary conditions :)

1
Indraneel Chatterjee ·

what if the question is this i have edited the question slightly pls check.

62
Lokesh Verma ·

this does not make much sense..

all u needed to say is that there exists a funciton..

f(x)=(px2 +6x-8)/(p+6x-8x2)

which is onto R

but the basic method will be the same..

atleast i cant think of any other way right now!

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