Question

Please help....find the equation of a line perpendicular to y=-1/5x+7 and has point (-9,0). I just need a reminder on how to do this.

Answer 1

Perpendicular lines mean they have opposite slopes.

\[y = - \frac{ 1 }{ 5 }x + 7\]
\[y = -\frac{ 5 }{ 1 }(-9) + 7 + 0\]

I believe that is right? I may be wrong.

Answer 2

your slope is right, the negative reciprocal of \(-\frac{1}{5}\) is \(5\)

Answer 3

So it should be, correct?

y = 5x + b
y = 5(-9) +0
y = -45

Answer 4

Two perpendicular lines with slopes \[m _{1} \space and \space m _{2}\]

then \[m _{1} \times m _{2} = -1\]

Answer 5

@satellite73 I am aware.

Answer 6

the equation is wrong however
you need \(y-y_1=m(x-x_1)\) with \(m=5, x_1=-9,y_1=0\)

Answer 7

y - y1 = m(x - x1)
y - 0 = 5(x - (-9)

Right, you're right. It's been awhile since I've done that.

Answer 8

now you have it
\[y=5x+9\]

Answer 9

now the slope of second line will be 5 as you have found out.

y= 5x + b
now using the point given (-9,0) plug it in the above equation

0 = 5(-9) + b; this will give you b = 45

So the equation of the line is y = 5x + 45

Answer 10

Last time I did this I was in middle school. Ha, even my memory is blurry.

Answer 11

sorry satellite the answer is \[y = 5x + 45\]

Answer 12

yes, you are right it is \(y=5x+45\)

Answer 13

y - y1 = m(x - x1)
y - 0 = 5[(x - (-9)]
y = 5 (x + 9)
y = 5x + 45

Yea, he's right Satelite.

Answer 14

Don't pick on us Rajee, today isn't our brightest of days when it comes to math. :P

Answer 15

you guys have a 100 and 75 rating I just a mole you guys are mountains

Answer 16

thank you guys this help me so much i did this just last night and i couldnt remember I just drew a blank. math is not very nice to me :)

Answer 17

Haha, yea, sometimes even the good mathematicians have brain farts!