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Question -

Find the conjugates of the following complex numbers:

(i) 4 – 5i

(ii) 1 / (3 + 5i)

(iii) 1 / (1 + i)

(iv) (3 – i)2 / (2 + i)

(v) [(1 + i) (2 + i)] / (3 + i)

(vi) [(3 – 2i) (2 + 3i)] / [(1 + 2i) (2 – i)]



Answer -

(i) 4 – 5i

Given:

4 – 5i

We know the conjugateof a complex number (a + ib) is (a – ib)

So,

The conjugate of (4 –5i) is (4 + 5i)

(ii) 1 / (3 + 5i)

Given:

1 / (3 + 5i)

Since the givencomplex number is not in the standard form of (a + ib)

Let us convert tostandard form by multiplying and dividing with (3 – 5i)

We get,

We know the conjugateof a complex number (a + ib) is (a – ib)

So,

The conjugate of (3 –5i)/34 is (3 + 5i)/34

(iii) 1 / (1 + i)

Given:

1 / (1 + i)

Since the givencomplex number is not in the standard form of (a + ib)

Let us convert tostandard form by multiplying and dividing with (1 – i)

We get,

We know the conjugateof a complex number (a + ib) is (a – ib)

So,

The conjugate of(1-i)/2 is (1+i)/2

(iv) (3 – i)2 /(2 + i)

Given:

(3 – i)2 /(2 + i)

Since the givencomplex number is not in the standard form of (a + ib)

Let us convert tostandard form,

We know the conjugateof a complex number (a + ib) is (a – ib)

So,

The conjugate of (2 –4i) is (2 + 4i)

(v) [(1 + i) (2 + i)] / (3+ i)

Given:

[(1 +i) (2 + i)] / (3 + i)

Since the givencomplex number is not in the standard form of (a + ib)

Let us convert tostandard form,

We know the conjugateof a complex number (a + ib) is (a – ib)

So,

The conjugate of (3 +4i)/5 is (3 – 4i)/5

(vi) [(3 – 2i) (2 + 3i)] /[(1 + 2i) (2 – i)]

Given:

[(3 –2i) (2 + 3i)] / [(1 + 2i) (2 – i)]

Since the givencomplex number is not in the standard form of (a + ib)

Let us convert tostandard form,

We know the conjugateof a complex number (a + ib) is (a – ib)

So,

The conjugate of (63– 16i)/25 is (63 + 16i)/25

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