Practicing Success
An energy DRONE is flying along the curve y = x2 + 7. A soldier is placed at (3, 7). The nearest distance of the DRONE from soldier’s position is |
2 3 \(\sqrt { 5}\) \(\sqrt { 7}\) |
\(\sqrt { 5}\) |
Let P(x, y) be position of the DRONE and the soldier is placed at A(3, 7). $AP=\sqrt{(x-3)^2+(y-7)^2}$ .....(i) $y = x^2 + 7$ .....(ii) since point lies on the curve $S=\sqrt{(x-3)^2+(x^2+7-7)^2}$ $S=\sqrt{x^4+x^2-6x+9}$ when distance is maximum/minimum $\frac{dS}{dx}=0⇒\frac{(4x^3+2x-6)}{\sqrt{(x^4+x^2-6x+9)}}=0$ $⇒4x^3+2x-6=0$ $⇒2x^3+x-3=0$ $⇒(x-1) × (2x^2+2x+3)$ The solution to above equation are $x = 1, -0.5 ± i × 0.5\sqrt{5}$ Since solution cannot have any complex roots. Hence, x = 1 is abscissa of the nearest point to the soldier. from eq. (i) we get, $y =1^2+7⇒y=8$ Nearest point is (1, 8) nearest distance $S = \sqrt{(1-3)^2+(8-7)^2}$ $S = \sqrt{(-2)^2+(1)^2}⇒S=\sqrt{4+1}$ $\Rightarrow S=\sqrt{5}$ |