4.1 Coordinates and Graphs

• Straight line graph
• Parallel and perpendicular lines
• Gradients of parallel and perpendicular lines

• plot out points on a Cartesian plane
• draw a straight-line graph given an equation
• draw parallel lines on the Cartesian plane
• relate the gradients of parallel lines
• draw perpendicular lines on the Cartesian plane
• relate the gradients of perpendicular lines
• apply graphs of straight lines in real-life situations

“How do we draw graphs of straight lines?”

“How do we interpret graphs of straight lines?”

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1. Points on the Cartesian plane
   40 min · 1 practice tasks · quiz
   A coordinate names a place with two numbers: across first, then up.
2. Drawing a line from its equation
   40 min · 1 practice tasks · quiz
   Make a table of values, plot the pairs, and join them with a ruler.
3. Parallel lines and their gradients
   40 min · 1 practice tasks · quiz
   Two lines are parallel exactly when their gradients are equal.
4. Perpendicular lines and their gradients
   40 min · 1 practice tasks · quiz
   Lines meet at a right angle exactly when their gradients multiply to minus one.
5. The line through a point, parallel or perpendicular
   40 min · 1 practice tasks · quiz
   Take the gradient from the relationship, then substitute the point to find c.
6. Straight-line graphs in real life
   40 min · 1 practice tasks · quiz
   On a real graph the intercept is the fixed charge and the gradient is the rate.