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If the line `x-1=0`is the directrix of the parabola `y^2-k x+8=0`, then one of the values of `k`is`1/8`(b) 8 (c) 4(d) `1/4`A. -8B. `1//8`C. `1//4`D. 4 |
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Answer» Correct Answer - A::D 1,4 We have equation of parabola, `y^(2)=kx-8ory^(2)=k(x-(8)/(k))` Equation of directrix is `x-(8)/(k)=-(k)/(4)orx=-(k)/(4)+(8)/(k)` Given equation of directrix is x=1. `:.(8)/(k)-(k)/(4)=1` `rArrk^(2)+4k-32=0` `rArr(k-4)(k+8)=0` `rArrk=-8,4` |
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