Stretch Rule 1 For $y=pf(x)$, $p \gt 0$, the effect of $p$ is to vertically stretch the graph by a factor by $p$. If $p \gt 1$, it moves points of $y=f(x)$ further away from the $x$-axis. If $0 \lt p \lt 1$, it moves points of $y=f(x)$ closer to the $x$-axis. Stretch Rule 2 […]

# Tag Archives: Sketching Graphs

# Reflections of Graphs

For $y=-f(x)$, we reflect $y=f(x)$ in the $x$-axis. For $y=f(-x)$, we reflect $y=f(x)$ in the $y$-axis. Example 1 Consider $f(x)=x^3-4x^2+4x$. On the same axes, sketch the graphs of $y=f(x)$ and $y=-f(x)$. \( \begin{align} \displaystyle f(x) &= x^3-4x^2+4x \\ &= x(x^2 – 4x + 4) \\ &= x(x-2)^2 \end{align} \) Example 2 Consider $f(x)=x^3-4x^2+4x$. On the […]

# Transformation of Rational Functions

Rational functions are characterised by the presence of both a horizontal asymptote and a vertical asymptote. Any graph of a rational function can be obtained from the reciprocal function $f(x)=\dfrac{1}{x}$ by a combination of transformations including a translation, stretches and compressions. $y=\dfrac{a}{x}$: horizontal compression, $0 \lt a \lt 1$ $y=\dfrac{a}{x}$: horizontal stretch, $a \gt 1$ […]

# Translations of Graphs

Translation Rule 1 For $y=f(x)+b$, the effect of $b$ is to translate the graph vertically through $b$ units. If $b \gt 0$, it moves upwards. If $b \lt 0$, it moves downwards. Translation Rule 2 For $y=f(x-a)$, the effect of $a$ is to translate the graph horizontally through $a$ units. If $a \gt 0$, it […]

# Reciprocal Functions

These techniques involves sketching the graph of $y=\dfrac{1}{f(x)}$ from the graph of $y=f(x)$. Technique 1 When $f(x)$ approaches towards $0$, $y=\dfrac{1}{f(x)}$ approaches towards $\infty$, the graph of $y=\dfrac{1}{f(x)}$ approaches the vertical asymptote(s). Technique 2 The graph of $y=\dfrac{1}{f(x)}$ has vertical asymptotes at the $x$-intercepts of $y=f(x)$. Technique 3 When $f(x)$ approaches towards $\infty$, $y=\dfrac{1}{f(x)}$ approaches […]

# Where Graphs Meet

Suppose we sketch the graphs of two functions $f(x)$ and $g(x)$ on the same axes. The $x$-coordinates of points where the graphs meet are the solutions to the equation $f(x)=g(x)$. We can use this property to solve equations graphically, but we must make sure the graphs are drawn carefully and accurately. Let’s take a look […]

# Intersections of Quadratic Graphs

Consider the graphs of a quadratic function and a linear function on the same set of axes. cutting2 points of intersection $b^2-4ac \gt 0$ touching1 point of intersection $b^2-4ac = 0$ missingno points of intersection $b^2-4ac \lt 0$ In the graphs meet, the coordinates of the points of intersection of the graphs can be found […]

# Finding Quadratics from Graphs

Example 1 Find the equation of the quadratic graph. \( \begin{align} \displaystyle y &= a(x+2)(x+1) \\ 2 &= a(0+2)(0+1) &\text{substitute }(0,2)\\ 2 &= 2a \\ a &= 1 \\ y &= 1(x+2)(x+1) \\ \therefore y &= x^2+3x+2 \\ \end{align} \) Example 2 Find the equation of the quadratic graph. \( \begin{align} \displaystyle y &= a(x+1)^2 […]

# Axis of Symmetry of Quadratic Graphs

The equation of the axis of symmetry of $y=ax^2+bx+c$ is $x=-\dfrac{b}{2a}$. Example 1 Find the equation of the axis of symmetry of $y=x^2+4x-2$. \( \begin{align} \displaystyle x &= -\dfrac{b}{2a} \\ &= -\dfrac{4}{2 \times 1} \\ \therefore x &= -2 \\ \end{align} \) Example 2 Find the equation of the axis of symmetry of $y=-2x^2-12x+3$. \( […]

# X-intercepts Y-intercepts

$x$-intercepts when $y=0$ $y$-intercepts when $x=0$ Example 1 Sketch the graphs of $y=x^2+x-2$ by stating $x$- and $y$-intercepts. $x$-intercepts when $y=0$ \( \begin{align} \displaystyle x^2+x-2 &= 0 \\ (x+2)(x-1) &= 0 \\ x &= -2, 1 \\ \end{align} \) $y$-intercepts when $x=0$ \( \begin{align} \displaystyle y &= 0^2+0-2 \\ &= -2 \\ \end{align} \) Example […]