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Exercises: Cubic Graphs and Graphical Solutions

Practice★☆☆
Let $f(x) = x^3 - 3x$. Copy and complete the table of values for $x = -2, -1, 0, 1, 2$.

Let $f(x) = x^3 - 3x$. Copy and complete the table of values for $x = -2, -1, 0, 1, 2$.

Solve
Practice★☆☆
The graph of $f(x) = x^3 - 4x$ crosses the $x$-axis at $x = -2$, $x = 0$ and $x = 2$. a) Write down the solutions of $f(x) = 0$. b) Write down the coordinates where the…

The graph of $f(x) = x^3 - 4x$ crosses the $x$-axis at $x = -2$, $x = 0$ and $x = 2$.

  1. a) Write down the solutions of $f(x) = 0$.
  1. b) Write down the coordinates where the graph crosses the $y$-axis.
Solve
Practice★☆☆
For $f(x) = x^3 - 3x + 1$, the graph passes through $(-2,-1)$, $(-1,3)$, $(0,1)$, $(1,-1)$ and $(2,3)$. Using these points, state which two consecutive integers each…

For $f(x) = x^3 - 3x + 1$, the graph passes through $(-2,-1)$, $(-1,3)$, $(0,1)$, $(1,-1)$ and $(2,3)$.

Using these points, state which two consecutive integers each root of $f(x) = 0$ lies between.

Solve
Practice★★☆
Let $f(x) = x^3 - 6x^2 + 9x$ for $0 \le x \le 4$. a) Complete a table of values for $x = 0, 1, 2, 3, 4$. b) Draw the graph of $f$ for $0 \le x \le 4$. c) Use your graph…

Let $f(x) = x^3 - 6x^2 + 9x$ for $0 \le x \le 4$.

  1. a) Complete a table of values for $x = 0, 1, 2, 3, 4$.
  1. b) Draw the graph of $f$ for $0 \le x \le 4$.
  1. c) Use your graph to estimate the solutions of $f(x) = 2$.
Solve
Practice★★☆
Let $f(x) = x^3 - 2x^2 - 5x + 6$ for $-3 \le x \le 4$. a) Complete a table of values for integer values of $x$ from $-3$ to $4$. b) Draw the graph of $f$. c) Use the…

Let $f(x) = x^3 - 2x^2 - 5x + 6$ for $-3 \le x \le 4$.

  1. a) Complete a table of values for integer values of $x$ from $-3$ to $4$.
  1. b) Draw the graph of $f$.
  1. c) Use the graph to write down the solutions of $f(x) = 0$.
Solve
Practice★★☆
Let $f(x) = x^3 - 3x$ for $-2 \le x \le 2$. On the same axes, draw the graph of $g(x) = x + 1$. a) Complete a table of values for both functions. b) Draw both graphs. c)…

Let $f(x) = x^3 - 3x$ for $-2 \le x \le 2$. On the same axes, draw the graph of $g(x) = x + 1$.

  1. a) Complete a table of values for both functions.
  1. b) Draw both graphs.
  1. c) Use your graphs to estimate the solutions of $x^3 - 3x = x + 1$ for $-2 \le x \le 2$.
Solve
Practice★★★
Let $f(x) = -x^3 + 3x^2 + 4$ for $-2 \le x \le 4$. a) Draw the graph of $f$ using integer values of $x$. b) Use your graph to estimate the solution of $f(x) = 0$. c)…

Let $f(x) = -x^3 + 3x^2 + 4$ for $-2 \le x \le 4$.

  1. a) Draw the graph of $f$ using integer values of $x$.
  1. b) Use your graph to estimate the solution of $f(x) = 0$.
  1. c) Find the range of values of $k$ for which $f(x) = k$ has three distinct real solutions, using $f'(x)$ to find the turning points.
Solve
Practice★★★
Let $f(x) = x^3 - 7x + 6$. a) Show that $x = 1$ is a root of $f(x) = 0$. b) Factorise $f(x)$ fully and write down all the roots. c) Sketch the graph of $f$, marking the…

Let $f(x) = x^3 - 7x + 6$.

  1. a) Show that $x = 1$ is a root of $f(x) = 0$.
  1. b) Factorise $f(x)$ fully and write down all the roots.
  1. c) Sketch the graph of $f$, marking the intercepts with both axes.
Solve
Practice★★★
A cubic function is $f(x) = x^3 + bx^2 + cx + d$. Its graph passes through $(0, 4)$, $(1, 0)$ and $(-1, 6)$. a) Find the values of $b$, $c$ and $d$. b) Show that $x = 1$…

A cubic function is $f(x) = x^3 + bx^2 + cx + d$. Its graph passes through $(0, 4)$, $(1, 0)$ and $(-1, 6)$.

  1. a) Find the values of $b$, $c$ and $d$.
  1. b) Show that $x = 1$ is a root and find the other roots of $f(x) = 0$, if any.
  1. c) Find the number of solutions of $f(x) = 4$.
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