Question

The number of integral value of l for which

x² + y² + 2l x + 2(1 –l)y –1 = 0 is the equation of a circle whose radius can not exceed 3

• A. 3
• B. 4
• C. 5
• D. None

Answer 1

Answer: (B)

4

Answer 2

$\sqrt { \lambda ^ { 2 } + ( 1 - \lambda ) ^ { 2 } + 1 }$< 3

l² + l² –2l + 1 + 1 < 9

2l² –2l – 7 < 0

$\frac { 1 + \sqrt { 15 } } { 2 }$

–1.45 < l < 2. 45

–1, 0, 1, 2