David W. answered 10/06/16
Tutor
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Experienced Prof
The Standard Format of the equation of a line is: Ax + By = C
You should, once and forever, convert that to the slope-intercept form for the equation of a line and remember that:
- the slope is (-A/B)
- the y-intercept is (C/B)
If both points (3,-12) and (-12,0) are on this line then:
A(3) + B(-12) = C = A(-12) + B(0)
3A -12B = -12A
15A = 12B
(-A/B) = -4/5 (the slope)
The equation has the form: 4x + 5y = C and we need one of the points to find C [use (-12,0)]
4(-12) + 5(0) = C
-48 = C
The equation is: 4x + 5y = -48 (in Standard Format)
Check:
Is 4(3) + 5(-12) = -48 ?
12 - 60 = -48 ?
-48 = -48 ?yes
Is 4(-12) + 5(0) = -48 ?
-48 = -48 ?yes