Question

Question 4 Express the given complex number in the form a + ib: 3(7 + i7) + i(7 + i7)

Class X1 - Maths -Complex Numbers and Quadratic Equations Page 104

Answer 1

3(7 +i7) +i(7 + i7)
= 3 × 7 + 3 × i7 + i7 +i²7
= 21 + 21i + i7 + 7i²
= 21 + (21 + 7)i + 7(-1)[ use, i²=-1]
= 21 + 28i - 7
= 14 + 28i

Hence, 14 + 28i is the answer.

Answer 2

To find :

• we need to express the given complex number in the form a + ib

Solution :

3(7 + i7) + i(7 + i7)

= 21 + 21i + 7i + 7i²

= 21 + 28i + 7 × (-1) [i² = -1]

= 21 - 7 + 28i

= 14 + 28i

━━━━━━━━━━━━━━━━━━━━━━━━━