JAMIA 2022 — Mathematics PYQ
JAMIA | Mathematics | 2022If 1, log9 (31-x+ 2) and log3 (4.3x –1) are in A.P., then x equals
Choose the correct answer:
- A. log34
- B. 1–log34(Correct Answer)
- C. 1–log43
- D. log43
1–log34
Explanation
1. Set Up the Equation
The given terms are 1, log9(31−x+2), and log3(4⋅3x−1).
Using the A.P. property:
2log9(31−x+2)=1+log3(4⋅3x−1)
2. Simplify the Logarithms
First, we change the base of the left side. Since 9=32, we use the property logan(b)=n1loga(b):
2⋅21log3(31−x+2)=1+log3(4⋅3x−1)
log3(31−x+2)=log3(3)+log3(4⋅3x−1)
Using the logarithmic addition property log(m)+log(n)=log(mn):
log3(31−x+2)=log3(3(4⋅3x−1))
Now, remove the logarithms from both sides:
31−x+2=3(4⋅3x−1)
3. Solve the Exponential Equation
Let 3x=y. Then 31−x=3x3=y3.
Substitute y into the equation:
y3+2=3(4y−1)
y3+2=12y−3
Multiply the entire equation by y to clear the fraction:
3+2y=12y2−3y
12y2−5y−3=0
4. Solve the Quadratic Equation
Using the quadratic formula or factoring:
12y2−9y+4y−3=0
3y(4y−3)+1(4y−3)=0
(3y+1)(4y−3)=0
Possible values for y:
-
y=−31 (Not possible since 3x must be positive)
-
y=43
5. Find x
Since 3x=y:
3x=43
Taking log3 on both sides:
x=log3(43)
x=log3(3)−log3(4)
x=1−log3(4)

