JAMIA 2021 — Mathematics PYQ
JAMIA | Mathematics | 2021If (1−i1+i)x=1, then
Choose the correct answer:
- A.
x=2n+1, where n∈N
- B.
x=4n, where n∈N
(Correct Answer) - C.
x=2n, where n∈N
x=4n, where n∈N
Explanation
Step 1: Simplify the expression inside the bracket
Multiply the numerator and the denominator by the conjugate of the denominator (1+i):
1−i1+i=1−i1+i×1+i1+i
1−i1+i=12−i2(1+i)2
1−i1+i=1−(−1)1+2i+i2
Since i2=−1:
1−i1+i=21+2i−1
1−i1+i=22i=i
Step 2: Substitute back into the original equation
The original equation (1−i1+i)x=1 becomes:
ix=1
Step 3: Solve for x
We know the powers of i:
-
i1=i
-
i2=−1
-
i3=−i
-
i4=1
The value of ix is 1 whenever x is a multiple of 4.
x=4n,where n∈Z
Explanation
Step 1: Simplify the expression inside the bracket
Multiply the numerator and the denominator by the conjugate of the denominator (1+i):
1−i1+i=1−i1+i×1+i1+i
1−i1+i=12−i2(1+i)2
1−i1+i=1−(−1)1+2i+i2
Since i2=−1:
1−i1+i=21+2i−1
1−i1+i=22i=i
Step 2: Substitute back into the original equation
The original equation (1−i1+i)x=1 becomes:
ix=1
Step 3: Solve for x
We know the powers of i:
-
i1=i
-
i2=−1
-
i3=−i
-
i4=1
The value of ix is 1 whenever x is a multiple of 4.
x=4n,where n∈Z

