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If lx + my + n = 0 is tangent to the parabola `x^(2)=y`, themA. `t^(2)=2mn`B. `i=4m^(2)n^(2)`C. `m^(2)=4/n`D. `l^(2)=4mn` |
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Answer» Correct Answer - D We know that x = my+x touche the parabola `x^(2)=4ay`, if `c=a/m`, Therefore , lx+my+n=0 or `x=-m/ly+-n/l` touches `x^(2)=y`, if `(-n)/l=((1//4))/((-m//l))rArr(mn)/l^(2)=1/4rArrl^(2)=4mn` `Delta"LITER"` If lx + my + n = 0 touches the parabola `x^(2)=y`, then `lx+mx^(2)+n=0` must have equal roots. `:." "l^(2)=4mn" [On equating discriminant to zero]"` |
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