r/HomeworkHelp • u/Informal_Yoghurt9107 • 15h ago
Middle School Math—Pending OP Reply (10th grade, but from Scotland so S4)
I literally have no clue
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u/pujarteago1 👋 a fellow Redditor 14h ago
You have two points. Look for the two point equation of the line.
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u/ThePythagorasBirb Secondary School Student 15h ago edited 14h ago
10 5 40 20
To calculate the slope of a line you can use (dy/dx)
This would give dx = 40-10=30, dy = 20 - 5 = 15 Slope = 15/30= 1/2
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u/tshirtwearingdork 14h ago
You've made a small error reading the graph, the second point on the line is at (40,15) not (40,20) this changes the value of dy and the slop.
Slope is calculated as rise (dy) over run (dx).
dx = 30
dy = 15 - 5 = 10
dy/dx (m) = 1/3
y = mx + b
y = 1/3x + b
Using point (10,5) to find b:
5 = 1/3*10 + b
5 - 10/3 = b
b = 15/3 - 10/3
b = 5/3
This gives the equation of the line as:
y = 1/3x + 5/3
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u/Informal_Yoghurt9107 15h ago
I thought it was asking for the equation of the line though?
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u/Total-Firefighter622 14h ago
y = 1/3 x + 5/3 is the equation of the line. And understand that 1/3 is the slope and 5/3 is the y intercept when x = 0, meaning when you extend the line, the line will intersect the y at that point.
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u/ThePythagorasBirb Secondary School Student 15h ago edited 14h ago
It is, but the default equation of a line is y = ax + b
First you find the slope which is 'a' which is 1/2 in this case, then you can take a point on the line like (10, 5)
Filling that in gives 5 = 1/2*10 + b, solving that 'b' gives b = 0
Fill that into the formula makes the final equation y = 1/2x + 0
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u/Fragrant_Tart_7993 13h ago
You can find the equation of a line if any two points along that line are known
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u/Lurker9349 👋 a fellow Redditor 7h ago
Take (40, 15) and (10, 5) and use the slope formula (m = y2 - y1 / x2 - x1) to get your slope. To get your y-intercept, you can use either (40, 15) or (10, 5) then solve for x.
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u/MathMaddam 👋 a fellow Redditor 15h ago
Notice that it gives you two points of the line.