PLZ PLZ HELP! Medal will be given!! Slope Intercept Form!

Question

anonymous · Answer

Write an equation in slope-intercept form of the line that passes through the given point and is perpindicular to the gaph of the given equation...

(1, -2); y = 5x + 4

So I know the answer is y = -1/5x - 9/5. But i just don't know how  my teacher got it...

anonymous · Answer

m= y2-y1 over x2-x1
or y=mx+b

anonymous · Answer

I know. but I don't know what I plug in for the equation! Because there's only one set of coordinates, (1, -2)

texaschic101 · Answer

do you know what the slope is in y = 5x + 4 ?

anonymous · Answer

No? I don't.

texaschic101 · Answer

In y = mx + b form, the slope is in the m position, therefore the slope of the equation given is 5. Do you understand that ?

anonymous · Answer

Okay, got it. Yes, I now understand that part...

texaschic101 · Answer

However, we are looking for a perpendicular line. So we need the negative reciprocal of the slope given. All that means is " flip " the slope and change the sign. The slope given is 5, and the slope we need is the negative reciprocal of 5 which is -1/5 (see how I flipped the lope and changed the sign). So we need slope -1/5...still with me ?

haseeb96 · Answer

y=5x+4
m=5
but here the conndition is perpendicular
so , m1m2=-1
5m2=-1
m2=-1\5
y=mx+b........eq#1
put it in the eq#1
(x,y)=(1,-2)

-2=-1\5 (1) +b
-10=-1+b

b=-9
so , eq#1 becomes
y=-x\5 -9

texaschic101 · Answer

typo * flipped the slope

haseeb96 · Answer

this is the correct answer

anonymous · Answer

Got it, still with you! @texaschic101 And thanks @Haseeb96 but my teacher said the correct answer was y = -1/5x - 9/5...

texaschic101 · Answer

now that we know the slope is -1/5, sub that in for m and your points (1,-2) x = 1 and y = -2...sub that into y = mx + b and find b
y = mx + b
-2 = -1/5(1) + b
-2 = -1/5 + b
-2 + 1/5 = b
-10/5 + 1/5 = b
-9/5 = b
so your perpendicular equation is : y = -1/5x - 9/5

texaschic101 · Answer

do you have any questions ?

haseeb96 · Answer

i have mistaken there

anonymous · Answer

Wow no! Thank you very much for helping me with that and made it easy to understand! @texaschic101

texaschic101 · Answer

no problem :)

anonymous · Answer

Oh haha no problem! @Haseeb96 Thank you very much as well! (:

haseeb96 · Answer

i forgot the one thing there that is LCM

anonymous · Answer

Well thank you anyways!