1.

The common tangent of the parabolas `y^(2)=4x" and "x^(2)=-8y,` isA. y=x+2B. y=x-2C. y=2x+3D. none of these

Answer» Correct Answer - D
The equation tangent to `y^(2)=4x" is "y=mx + 1/m`
If it touches `x^(2)=-8y` then the equation `x^(2)=-8(mx=1/m)` must have equal roots.
`rArr" "64m^(3)=32rArr,(1/2)^("1/3")`
Hence, the equation of the common tangent is `y=x/(2^("1/3"))+2^("1/3")`


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