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21 votes
21 votes
Perpendicular to the line y= 1/4x -9; passes through (1,1)

User Zhuochen Shen
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1 Answer

15 votes
15 votes

Let:


m1=(1)/(4)

The slope of the line y = 1/4x - 9


m2

The slope of the unknown line.

If two lines are perpendicular, it is true:


\begin{gathered} m1\cdot m2=-1 \\ (1)/(4)\cdot m2=-1 \\ solve_{\text{ }}for_{\text{ }}m2\colon \\ m2=-4 \end{gathered}

Let:


(x1,y1)=(1,1)

Using the point-slope equation:


\begin{gathered} y-y1=m2(x-x1) \\ y-1=-4(x-1) \\ y-1=-4(x-1) \\ y-1=-4x+4 \\ y=-4x+4+1 \\ y=-4x+5 \end{gathered}

User BNT
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2.5k points