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If 3 = a + b be an identify, then the value of b is : (x + 2)(2x + 1) 2x + 1 x + 2
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- 0
- –1
- 2
- 3
Correct Option: B
| = | + | ||||
| (x + 2)(2x + 1) | 2x + 1 | x + 2 |
| ⇒ | = | ||
| (x + 2)(2x + 1) | (2x + 1)(x + 2) |
⇒ 3 = ax + 2a + 2bx + b
⇒ 3 = ax + 2bx + 2a + b
⇒ 3 = x (a + 2b) + (2a + b)
On comparing the respective co– efficients,
a + 2b = 0
⇒ a = – 2b ..... (i)
and, 2a + b = 3 2 (– 2b) + b = 3
⇒ – 4b + b = 3
| ⇒ – 3b = 3 ⇒ b = | = - 1 | |
| 3 |
