For What Value Of λ Will The Line y = 2x + λ Be A Tangent To The Circle x2 +y2 = 5?

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Question

For what value of λ will the line = 2x + λ be a tangent to the circle x2 +y2 = 5?

Solution

Correct option is

± 5

 

Comparing the given line with y = mx + c, we get

m = 2, c = λ and given circle with x2 + y2 = a2

then                       a2 = 5

∵ Condition for tangency is

                 

                 λ2 = 25

∴               λ = ± 5.

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