Question 449344
A line passes through the point (1,3) and has a slope of 4. Write an equation for the line.
Use the point/slope form to find this equation, (y - y1 = m(x - x1)
Where, in this equation, m=4, x1=1, y1=3
y - 3 = 4(x - 1)
y - 3 = 4x - 4
y = 4x - 4 + 3
y = 4x - 1, is the equation of this line
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Find the equation of the line that is perpendicular to the first line and passes through (1,3).
The slope relationship of perpendicular lines: m1*m2 = -1
let m1 = 4, find m2
4*m2 = -1
Divide both sides by 4
m2 = {{{-1/4}}}, is the slope of the perpendicular line
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Using the point/slope again, find the equation for the perpendicular line
y - 3 = {{{-1/4}}}(x - 1)
y - 3 = {{{-1/4}}}x + {{{1/4}}}
y = {{{-1/4}}}x + {{{1/4}}} + 3
y = {{{-1/4}}}x + {{{1/4}}} + {{{12/4}}}
y = {{{-1/4}}}x + {{{13/4}}}, is the line perpendicular to y=4x-1 and passes thru point 1, 3
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Graphically 
{{{ graph( 300, 300, -5, 5, -5, 5, 4x-1, -.25x+3.25) }}}
Note that lines intersect at 1, 3
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How about this; was it understandable to you? Any questions?