Graphs

Graphs

1. Algebraic graphs

   • y=mx+c
     • m is gradient
     • c is y intercept
   • 1. Make a table for x and y
   • 2. Plot onto graph
   • To find equation from graph
     • 1. pick 2 points on line
       • formula(s)
         • gradient = difference in y value / difference in x value
         • gradient = distance up triangle / distance across triangle
     • 2. Put m and c into y=mx+c
   • Quadratic graphs
     • Always parabolas
     • Can be written y = ax2+bx+c
   • Cubic and reciprocal graphs
     • y = ax^3+bx^2+cx+d
     • Where x is the bottom of the fraction

2. Real life graphs

   • Distance / time graphs
     • Distance on y axis
     • Gradient represents speed
       • Horizontal = stopped
       • Sloping up = Going away
       • Sloping down = Coming back
       • Steeper the line, faster the speed
   • Speed / time graphs
     • Time is always plotted on the x axis
     • Gradient represents acceleration
       • Horizontal = Constant speed
       • Sloping up = Accelerating
       • Sloping down = Slowing down
       • Steeper the line, quicker the acceleration

3. Representing data

   • Bar charts
   • Line graphs
   • Frequency polygons
   • Cumulative frequency graphs
   • Scatter diagrams