Question

The tangent at A (2, 4) on y = $x^3$ -2$x^2$ + 4 cuts the x axis at T then AT =

• A. 4
• B.
• C.
• D. 17

Answer 1

The correct option is C

$\frac{dy}{dx}=m=3x^2-4x=12-8=4$

$AT=\left|\frac{y_1\sqrt{1+m^2}}{m}\right|=\frac{4.\sqrt{17}}{4}=\sqrt{17}$