Sketch the graph of the polynomial function $$ p(x) = -2x^5-2x^4+7x^3+13 $$

Tap the blue points to see coordinates.

STEP 1:Find the x-intercepts

To find the x-intercepts solve, the equation $ \color{blue}{ -2x^5-2x^4+7x^3+13 = 0 } $

The solutions of this equation are:

$$ \begin{matrix}x_1 = -1.2727 & x_2 = 1.7349 & x_3 = -2.2916 \end{matrix} $$

(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) = -2x^5-2x^4+7x^3+13 } $, so:

$$ \text{Y inercept} = p(0) = 13 $$

STEP 3:Find the end behavior

The end behavior of a polynomial is the same as the end behavior of a leading term.

$$ \lim_{x \to -\infty} \left( -2x^5-2x^4+7x^3+13 \right) = \lim_{x \to -\infty} -2x^5 = \color{blue}{ \infty } $$

The graph starts in the upper-left corner.

$$ \lim_{x \to \infty} \left( -2x^5-2x^4+7x^3+13 \right) = \lim_{x \to \infty} -2x^5 = \color{blue}{ -\infty } $$

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) $:

$$ p^{\prime} (x) = -10x^4-8x^3+21x^2 $$

The x coordinate of the turning points are located at the zeros of the first derivative

$$ p^{\prime} (x) = 0 $$ $$ \begin{matrix}x_1 = 0 & x_2 = 1.1033 & x_3 = -1.9033 \end{matrix} $$

(cleck here to see a explanation of how to solve the equation)

To find the y coordinates, substitute the above values into $ p(x) $

$$ \begin{aligned} \text{for } ~ x & = \color{blue}{ 0 } \Rightarrow p\left(0\right) = \color{orangered}{ 13 }\\[1 em] \text{for } ~ x & = \color{blue}{ 1.1033 } \Rightarrow p\left(1.1033\right) = \color{orangered}{ 16.168 }\\[1 em] \text{for } ~ x & = \color{blue}{ -1.9033 } \Rightarrow p\left(-1.9033\right) = \color{orangered}{ -11.5558 }\end{aligned} $$

So the turning points are:

$$ \begin{matrix} \left( 0, 13 \right) & \left( 1.1033, 16.168 \right) & \left( -1.9033, -11.5558 \right)\end{matrix} $$

STEP 5:Find the inflection points

The inflection points are located at zeroes of second derivative. The second derivative is $ p^{\prime \prime} (x) = -40x^3-24x^2+42x $.

The zeros of second derivative are

$$ \begin{matrix}x_1 = 0 & x_2 = 0.7677 & x_3 = -1.3677 \end{matrix} $$

Substitute the x values into $ p(x) $ to get y coordinates

$$ \begin{aligned} \text{for } ~ x & = \color{blue}{ 0 } \Rightarrow p\left(0\right) = \color{orangered}{ 13 }\\[1 em] \text{for } ~ x & = \color{blue}{ 0.7677 } \Rightarrow p\left(0.7677\right) = \color{orangered}{ 14.9392 }\\[1 em] \text{for } ~ x & = \color{blue}{ -1.3677 } \Rightarrow p\left(-1.3677\right) = \color{orangered}{ -2.3359 }\end{aligned} $$

So the inflection points are:

$$ \begin{matrix} \left( 0, 13 \right) & \left( 0.7677, 14.9392 \right) & \left( -1.3677, -2.3359 \right)\end{matrix} $$

Graphing Polynomials