Tap the blue points to see coordinates.
STEP 1:Find the x-intercepts
To find the x-intercepts solve, the equation $ \color{blue}{ -x^3+400x^2-290x-1800 = 0 } $
The solutions of this equation are:
$$ \begin{matrix}x_1 = -1.7863 & x_2 = 2.5239 & x_3 = 399.2624 \end{matrix} $$(you can use the step-by-step polynomial equation solver to see a detailed explanation of how to solve the equation)
STEP 2:Find the y-intercepts
To find the y-intercepts, substitute $ x = 0 $ into $ \color{blue}{ p(x) = -x^3+400x^2-290x-1800 } $, so:
$$ \text{Y inercept} = p(0) = -1800 $$STEP 3:Find the end behavior
The end behavior of a polynomial is the same as the end behavior of a leading term.
$$ \lim_{x \to -\infty} \left( -x^3+400x^2-290x-1800 \right) = \lim_{x \to -\infty} -x^3 = \color{blue}{ \infty } $$The graph starts in the upper-left corner.
$$ \lim_{x \to \infty} \left( -x^3+400x^2-290x-1800 \right) = \lim_{x \to \infty} -x^3 = \color{blue}{ -\infty } $$The graph ends in the lower-right corner.
STEP 4:Find the turning points
To determine the turning points, we need to find the first derivative of $ p(x) $:
$$ p^{\prime} (x) = -3x^2+800x-290 $$The x coordinate of the turning points are located at the zeros of the first derivative
$$ p^{\prime} (x) = 0 $$ $$ \begin{matrix}x_1 = 266.3037 & x_2 = 0.363 \end{matrix} $$(cleck here to see a explanation of how to solve the equation)
To find the y coordinates, substitute the above values into $ p(x) $
$$ \begin{aligned} \text{for } ~ x & = \color{blue}{ 266.3037 } \Rightarrow p\left(266.3037\right) = \color{orangered}{ 9402400.7584 }\\[1 em] \text{for } ~ x & = \color{blue}{ 0.363 } \Rightarrow p\left(0.363\right) = \color{orangered}{ -1852.6102 }\end{aligned} $$So the turning points are:
$$ \begin{matrix} \left( 266.3037, 9402400.7584 \right) & \left( 0.363, -1852.6102 \right)\end{matrix} $$STEP 5:Find the inflection points
The inflection points are located at zeroes of second derivative. The second derivative is $ p^{\prime \prime} (x) = -6x+800 $.
The zero of second derivative is
$$ \begin{matrix}x = \dfrac{ 400 }{ 3 } \end{matrix} $$Substitute the x value into $ p(x) $ to get y coordinates
$$ \begin{aligned} \text{for } ~ x & = \color{blue}{ \frac{ 400 }{ 3 } } \Rightarrow p\left(\frac{ 400 }{ 3 }\right) = \color{orangered}{ \frac{ 126907400 }{ 27 } }\end{aligned} $$So the inflection point is:
$$ \begin{matrix} \left( \dfrac{ 400 }{ 3 }, \dfrac{ 126907400 }{ 27 } \right)\end{matrix} $$