1.

If the line joining the points `(0,3)a n d(5,-2)`is a tangent to the curve `y=C/(x+1)`, then the value of `c`is1 (b) `-2`(c) 4(d) none of theseA. 1B. -2C. 4D. none of these

Answer» Correct Answer - C
The equation of the line joining (0,3) and (5,-2) is
` x+y-3=0 " "…(i) `
Suppose this line touches the curve `y=(C )/(x+1) " at " (alpha, beta ).` Then,
` ((dy)/(dx))_((alpha"," beta)) =` Slope of the line (i)
` rArr -(C)/((alpha+1)^(2))=-1 " "[ because (dy)/(dx)=- (C)/((x+1)^(2))]`
` rArr C=(alpha+1)^(2) " "...(ii) `
Also, ` (alpha,beta)` lies on the line (i) and the given curve. Therefore,
` alpha+ beta -3=0 " "...(iii) `
and, ` beta=(C)/(alpha+1) " "...(iv) `
Form (ii) and (iv), we get
` beta=alpha+1 " "...(v) `
Solving (iii) and (v), we get
` 2 alpha +1-3 =0 rArr alpha =1 `
Substituting ` alpha=1 ` in (ii), we get C = 4


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