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Objective. Understand that all straight line graphs can be represented in the form y=mx+c, and be able to state the equation of given graphs. All straight lines can be written in the form y = mx + c. Knowledge:.
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Objective Understand that all straight line graphs can be represented in the form y=mx+c, and be able to state the equation of given graphs
All straight lines can be written in the formy = mx + c Knowledge: You need to be able to write down the equation of a straight line by working out the values for m and c. It’s not as hard as you might think!
y = mx + c c is the constant value – this part of the function does not change. m is the gradient of the line Why use m? This type of equation was made popular by the French Mathematician Rene Descartes. “m” could stand for “Monter” – the French word meaning “to climb”.
Finding m and c 8 7 6 y 5 4 3 2 1 1 2 3 4 5 6 7 8 –7 –6 –5 –4 –3 –2 –1 -1 -2 -3 -4 -5 -6 x Look at the straight line. It is very easy to find the value of c – this is the point at which the line crosses the y-axis So c = 3 Finding m is also easy in this case. The gradient means the rate at which the line is climbing. Each time the lines moves 1 place to the right, it climbs up by 2 places. y = 2x +3 y = mx +c So m = 2
Another example We can see that c = -2 8 7 6 y 5 4 3 2 1 1 2 3 4 5 6 7 8 –7 –6 –5 –4 –3 –2 –1 -1 -2 -3 -4 -5 -6 x As the line travels across 1 position, it is not clear how far up it has moved. But… Any right angled triangle will give use the gradient! Let’s draw a larger one. In general, to find the gradient of a straight line, we divide the… vertical change by the… horizontal change. The gradient, m = 2/4 =½ 2 y = mx +c y = ½x - 2 4
Plenary: Assessing ourselves 8 7 6 y 5 4 3 2 1 1 2 3 4 5 6 7 8 –7 –6 –5 –4 –3 –2 –1 -1 -2 -3 -4 -5 -6 x y = 2x + 4 y = 2x - 3 y = 3x + 2 y = -2x + 6 y = x + 3 y = 4 y = 4x + 2 y = -x + 2 x = 2
Did you meet the objective? Understand that all straight line graphs can be represented in the form y=mx+c, and be able to state the equation of given graphs