JAMIA 2022 — Mathematics PYQ
JAMIA | Mathematics | 2022If x, 2x + 2, 3x + 3 are in G.P., then the 4th term is
Choose the correct answer:
- A.
12
- B.
12.5
- C.
13
- D.
13.5
(Correct Answer)
13.5
Explanation
Step 1: Find the value of x
If three terms a,b,c are in G.P., then the middle term squared is equal to the product of the other two:
b2=ac
Given the terms x,(2x+2),(3x+3), we set up the equation:
(2x+2)2=x(3x+3)
Expand both sides:
(2(x+1))2=3x(x+1)
4(x+1)2=3x(x+1)
Step 2: Solve the Equation
We can rearrange the equation to one side:
4(x+1)2−3x(x+1)=0
Factor out (x+1):
(x+1)[4(x+1)−3x]=0
(x+1)[4x+4−3x]=0
(x+1)(x+4)=0
This gives two possible values for x:
-
x=−1
-
x=−4
Note: If x=−1, the terms become −1,0,0. In a standard G.P., terms are usually non-zero, so we proceed with x=−4.
Step 3: Determine the Terms and Common Ratio
Substitute x=−4 into the expressions:
-
First term (a1) = x=−4
-
Second term (a2) = 2(−4)+2=−8+2=−6
-
Third term (a3) = 3(−4)+3=−12+3=−9
Now, find the common ratio (r):
r=a1a2=−4−6=23=1.5
Verify with the third term:
−6×1.5=−9
(Correct)
Step 4: Find the 4th Term
The fourth term (a4) is the third term multiplied by the common ratio:
a4=a3×r
a4=−9×23
a4=−227=−13.5

