CUET Preparation Today
The values of b for which $y=2x^2-bx+2$ touches the x-axis are : |
2, -6 0 ±5 ±4 |
±4 |
The correct answer is Option (4) → ±4 $y=2x^2-bx+2$ ...(1) y touches x axis when $\frac{dy}{dx}=0$ and $y=0$ from (1) at touch point $2x^2-bx+2=0$ $2(\frac{b}{4})^2-b(\frac{b}{4})+2=0$ $⇒\frac{b^2}{8}-\frac{b^2}{4}+2=0⇒2=\frac{b^2}{8}$ $⇒b=±4$ |
