Sketch the graph of the polynomial function $$ p(x) = x^4+2x^3-53x^2-54x+504 $$

Tap the blue points to see coordinates.

STEP 1:Find the x-intercepts

To find the x-intercepts solve, the equation $ \color{blue}{ x^4+2x^3-53x^2-54x+504 = 0 } $

The solutions of this equation are:

$$ \begin{matrix}x_1 = 3 & x_2 = 6 & x_3 = -4 & x_4 = -7 \end{matrix} $$

(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^4+2x^3-53x^2-54x+504 } $, so:

$$ \text{Y inercept} = p(0) = 504 $$

STEP 3:Find the end behavior

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

$$ \lim_{x \to -\infty} \left( x^4+2x^3-53x^2-54x+504 \right) = \lim_{x \to -\infty} x^4 = \color{blue}{ \infty } $$

The graph starts in the upper-left corner.

$$ \lim_{x \to \infty} \left( x^4+2x^3-53x^2-54x+504 \right) = \lim_{x \to \infty} x^4 = \color{blue}{ \infty } $$

The graph ends in the upper-right corner.

STEP 4:Find the turning points

To determine the turning points, we need to find the first derivative of $ p(x) $:

$$ p^{\prime} (x) = 4x^3+6x^2-106x-54 $$

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

$$ p^{\prime} (x) = 0 $$ $$ \begin{matrix}x_1 = -\dfrac{ 1 }{ 2 } & x_2 = 4.7202 & x_3 = -5.7202 \end{matrix} $$

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

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

$$ \begin{aligned} \text{for } ~ x & = \color{blue}{ -\frac{ 1 }{ 2 } } \Rightarrow p\left(-\frac{ 1 }{ 2 }\right) = \color{orangered}{ \frac{ 8281 }{ 16 } }\\[1 em] \text{for } ~ x & = \color{blue}{ 4.7202 } \Rightarrow p\left(4.7202\right) = \color{orangered}{ -225 }\\[1 em] \text{for } ~ x & = \color{blue}{ -5.7202 } \Rightarrow p\left(-5.7202\right) = \color{orangered}{ -225 }\end{aligned} $$

So the turning points are:

$$ \begin{matrix} \left( -\dfrac{ 1 }{ 2 }, \dfrac{ 8281 }{ 16 } \right) & \left( 4.7202, -225 \right) & \left( -5.7202, -225 \right)\end{matrix} $$

STEP 5:Find the inflection points

The inflection points are located at zeroes of second derivative. The second derivative is $ p^{\prime \prime} (x) = 12x^2+12x-106 $.

The zeros of second derivative are

$$ \begin{matrix}x_1 = 2.5139 & x_2 = -3.5139 \end{matrix} $$

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

$$ \begin{aligned} \text{for } ~ x & = \color{blue}{ 2.5139 } \Rightarrow p\left(2.5139\right) = \color{orangered}{ 105.0278 }\\[1 em] \text{for } ~ x & = \color{blue}{ -3.5139 } \Rightarrow p\left(-3.5139\right) = \color{orangered}{ 105.0278 }\end{aligned} $$

So the inflection points are:

$$ \begin{matrix} \left( 2.5139, 105.0278 \right) & \left( -3.5139, 105.0278 \right)\end{matrix} $$

Graphing Polynomials