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Find the equation of the line that passes through points (7,3) and (-2,9)?
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First, calculate the slope.
The formula for the slope of a straight line passing through two given points (,) and (,) is
m = .
Substitute the given data =7, = 3, = -2, = 9 into this basic formula
m = = = .
Next, find an equation of the line having the slope 3 and passing through the given point (7,3).
An equation of a straight line in a coordinate plane which has the slope m and passes through the given point P = (a,b) is
y - b = m*(x-a).
Substitute here m = , a = 7, b = 3, and you will get
y - 3 = . (*)
It is the equation in the slope-point form.
If you want to have it in the general form, transform it in this way
3y -9 = (-2)*(x-7) (after multiplying both sides of (*) by 3), or
3y -9 = -2x + 14, and finally
3y + 2x = 23.
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See the lesson
- Equation for a straight line in a coordinate plane passing through two given points
in this site.