The number of tangents to the curve $xy-3y+2=0$ having slope 2 is: |
0 1 2 Infinite |
2 |
The correct answer is Option (3) → 2 Given curve $xy-3y+2=0$ Differentiate implicitly w.r.t. $x$ $x\frac{dy}{dx}+y-3\frac{dy}{dx}=0$ Group terms $(x-3)\frac{dy}{dx}+y=0$ $\frac{dy}{dx}=\frac{-y}{x-3}$ Given slope $=2$ $2=\frac{-y}{x-3}$ $y=-2(x-3)$ $y=-2x+6$ This line must touch the curve, so substitute in curve equation $x(-2x+6)-3(-2x+6)+2=0$ $-2x^2+6x+6x-18+2=0$ $-2x^2+12x-16=0$ $x^2-6x+8=0$ Discriminant $D=36-32=4>0$ Two real and distinct points of contact exist. Number of tangents $=2$ |