Help with these:/ I don't understand

- anonymous

Help with these:/ I don't understand

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- anonymous

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- hartnn

can you find slope of any given line ?

- hartnn

like say , x-5y = -10 is a line.
can you find slope of this line first ?

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## More answers

- anonymous

Uh no not really... with a quick review I probably can

- hartnn

good,
so i have x-5y =-10
i will try to isolate y and bring it in the form y=mx+c where m=slope
so,
x=5y-10
5y = x+10
y= (1/5)x +2
got this ?

- anonymous

Yeah I got it

- hartnn

cool, so can you find the slope of x -3y=9 line ? in same way

- hartnn

oh and i forgot to mention,
y= (1/5)x +2
comparing with y=mx+c
gives, m=slope = 1/5

- anonymous

x-37=9
-3y=x+9
Y=(1/3)x+3

- anonymous

So slope would be 1/3 I assume?

- hartnn

correct! :)
now try to find slopes of other 3 lines also!
and tell me, so that i will verify :)

- anonymous

4x+2y=5
2y=-4x+5
Y-(-1/2)x+2.5 ?

- hartnn

2y=-4x+5 is correct, but then divide both sides by 2
what u get ?

- anonymous

10x-5y=8
-5y=10x+8
Y=-2x+1.6?

- hartnn

10x-5y=8
-5y=10x+8 <<<<<

- anonymous

and you would get y=-2+2.5

- anonymous

Ahh okay -10 so the problem would come out with a positive 2x

- hartnn

yes, so the slope will be m= 2 , right ?

- anonymous

Yes

- hartnn

4x+2y=5 slope = -2
make a note of all slopes, we'll need them

- hartnn

and what about last line ?

- anonymous

4x+y=-1
Y=-4x-1

- hartnn

so, slope =?

- anonymous

-4

- hartnn

Good!
now here's the rule :
slope of parallel lines are equal!
so, for the last one, slope of line parallel to 4x+y=-1 will also be m=-4 :)
so, for last, the correct option will be `C) m=-4`
got this ?
in same way, can you match the 2nd last and 3rd last ?

- anonymous

Yeah I got it, Thanks a ton man. You need to be my teacher xD

- hartnn

haha, :)
but we still require to do the 1st 2 !

- hartnn

another rule,
`product of slopes of perpendicular lines = -1 `
so, for 1st one we had slope = 1/5
let slope of perpendicular line be m.
so,
\(\Large m\times (1/5)=-1\)
find m from here :)

- anonymous

1st one is m=1/5?
2cnd one is m=1/3?
It seems like these would be the answers but they are not possible to be selected.

- anonymous

Ahhhh okay

- hartnn

because perpendicular lines follow different rule :)

- anonymous

Well I still don't exactly get how it goes from (1/5) to -1...

- hartnn

product of slopes = -1 is the rule
so, m (1/5) =-1
multiplying by 5,
m = -5
got this ?

- hartnn

multiplying by 5 on both sides.

- anonymous

I'm confused on the product of slopes part, I get the multiplying on both sides. So like can you explain the product of slopes rule.. I tried looking it up on google but nothing I can comprehend really comes up.

- hartnn

if say line 1 has slope M1
and line 2 has slope M2
now if these 2 lines are perpendicular to each other, then M1*M2 =-1

- hartnn

another way to remember the same thing is, the slope of line is negative reciprocal of the perpendicular line,
so, slope of line perpendicular to line with slope 1/5 will be - (1/(1/5)) = -5

- hartnn

so, thats your 1st one, m =-5
for 2nd one, we had slope = 1/3, so
m *(1/3) = -1
so, m=-3 is the answer to 2nd one :)

- anonymous

Okay, so basically whenever there is a fraction just take (1/_) blank space number lol

- hartnn

you forgot the negative :P
-1/ stuff

- hartnn

but this only applies to perpendicular lines

- hartnn

for parallel lines, slope are equal

- anonymous

Oh I see says the blind man

- hartnn

what who ?

- hartnn

lol

- hartnn

i hope you got the entire problem clearly ?

- hartnn

ask if any doubts anywhere

- anonymous

Yeah I get it now man thanks a ton

- hartnn

welcome ^_^

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