# Straight line graphs

### Description

GCSE Maths (Graphs) Mind Map on Straight line graphs, created by lizabeth rawson on 11/17/2019.
Mind Map by lizabeth rawson, updated more than 1 year ago
 Created by lizabeth rawson about 4 years ago
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## Resource summary

Straight line graphs
1. If an equations has y and/or x but no higher power (eg x², X³) then it's a straight line equation
1. Vertical and horizontal lines
1. x=a is a vertical line crossing a on the x-axis
1. y=a is a horizontal line through a on the y-axis
1. gradient of a line is how steep it is the larger the gradient the steeper the slope
1. a negative gradient means the slope is downhill
2. to find the gradient change in y _________________ change in x
3. Example
1. Point a = (6,50) and point b = (1,10)
1. the change in y = 50 - 10 = 40
1. the change in x = 6-1 = 5
1. gradient = 40/5 = 8
2. y = mx + c
1. m = gradient of line
1. c= y intercept
1. Example
1. equation of this line is y = 1/2 x + 15
2. Example 2
1. If you're given two points and on a line you can find the gradient and then you can use the gradient and one of the points to find the equation of the line
1. QUESTION: Find the equation of the straight line that passes through (-2,9) and (3,-1
1. M = change in y __________ change in x
1. which is -1 - 9 __________ 3 - -2
1. which is -10 ____________ 5
1. which is -2
2. substitute one of the points into the question you just found (eg (-2,9)
1. 9 = -2 (-2) + c
1. which is 9= 4 + c
1. c = 9-4
1. c = 5
2. substitute back into the formula, y = -2x + 5

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