Question Details

Consider the equation

1e(logex)12x(a(logex)32)2dx = 1

, where a(,0)(1,).
Which of the following statements is/are TRUE ?

Options

A

No a satisfies the above equation

B

An integer a satisfies the above equation

C

An irrational number a satisfies the above equation

D

More than one a satisfy the above equation.

Show Answer

Correct Answer :

Option C

An irrational number a satisfies the above equation

Option D

More than one a satisfy the above equation.

Solution :

Correct Statements:
1. An irrational number a satisfies the above equation
2. More than one a satisfy the above equation.

Let us evaluate the given definite integral step-by-step and determine all possible real values of a that satisfy the equation.

The given integral equation is:

1e(logex)12x(a(logex)32)2dx=1

Step 1: Use Substitution Method
Let t=logex. Then, its derivative with respect to x is:

dt=1xdx

Now, change the limits of integration according to t:

- When x=1, t=loge1=0.
- When x=e, t=logee=1.

Substituting t and dt into the integral gives:

01t12(at32)2dt=1

Step 2: Perform a Second Substitution
Let u=at32.
Differentiating both sides gives:

du=32t12dtt12dt=23du

Now, update the limits of integration for u:

- When t=0, u=a032=a.
- When t=1, u=a132=a1.

Substituting u and du into the integral:

aa123duu2=1

Reversing the limits of integration to absorb the negative sign:

23a1a1u2du=1

Step 3: Integrate and Solve for a
The antiderivative of 1u2 is 1u. Evaluating this between the limits:

23[1u]a1a=1

23(1a(1a1))=1

23(1a11a)=1

Combine the fractions inside the parentheses:

23(a(a1)a(a1))=1

23(1a2a)=1

Cross-multiplying gives:

a2a=23

3a23a2=0

Step 4: Analyze the Roots of the Quadratic Equation
Using the quadratic formula a=b±b24ac2a:

a=3±(3)24(3)(2)2(3)=3±9+246=3±336

Since 33 is irrational, both roots:

a1=3+336 and a2=3336

are irrational numbers.

Step 5: Check Domain Constraints
The given domain is a(,0)(1,).

- Since 5<33<6:
- a1=3+336>3+56=86>1, so a1(1,).
- a2=3336<356=26<0, so a2(,0).

Both roots lie completely within the allowed domain. Thus, there are two distinct irrational values of a that satisfy the equation.

Therefore, the true statements are:

1. An irrational number a satisfies the above equation
2. More than one a satisfy the above equation.

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