Q. 135.0( 2 Votes )

# If the circle x<s

Given that the circle x2 + y2 + 2ax + 8y + 16 = 0 touches x - axis. We need to find the value of a.

We know that the value of y on the x - axis is 0.

x2 + (0)2 + 2ax + 8(0) + 16 = 0

x2 + 2ax + 16 = 0

The quadratic equation will have similar roots if the circle touches the x - axis.

We know that for the quadratic equation ax2 + bx + c = 0 the condition to be satisfied for the equal roots is b2 - 4ac = 0

(2a)2 - 4(1)(16) = 0

4a2 - 64 = 0

a2 = 16

a = ±4

The correct option is (b).

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