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 jl1974 August 17th, 2017 12:26 PM

Straight Line workings

Hi,

Need help with the following please:

equation is Y=3x -1

I have two rows X and Y and trying to work the answers for the Y coordinate, struggling when I get to the minus figures.

X -3 -2 -1 0 1 2 3
Y ? ? ? -1 2 5 8

What are the (Y) answers for -1, -2 and -3

To get the first answer 8, I done 3x3-1 =8 and 3x2-1 = 5

Many thanks

 romsek August 17th, 2017 12:34 PM

Quote:
 Originally Posted by jl1974 (Post 577923) Hi, Need help with the following please: equation is Y=3x -1 I have two rows X and Y and trying to work the answers for the Y coordinate, struggling when I get to the minus figures. X -3 -2 -1 0 1 2 3 Y ? ? ? -1 2 5 8 What are the (Y) answers for -1, -2 and -3 To get the first answer 8, I done 3x3-1 =8 and 3x2-1 = 5 Many thanks
just continue as you have done

for $x=-1$

$y = 3(-1) - 1 = -3 -1 = -4$

I'm sure you can continue for $x=-2,~-3$

 jl1974 August 17th, 2017 12:48 PM

Thanks for response.

This is for my daughter, can you explain like my example if possible please.

like 3 times 3 = 9 minus 1 = 8

Can you tell me what the answer is for -1?

Thanks.

 cjem August 17th, 2017 02:47 PM

Quote:
 Originally Posted by jl1974 (Post 577926) 3 times 3 = 9 minus 1 = 8
Be careful how you use equals signs - it is not true that 3 times 3 equals 9 minus 1. You could instead separately state that 3 times 3 = 9, and that 9 minus 1 = 8.

 romsek August 17th, 2017 04:00 PM

Quote:
 Originally Posted by jl1974 (Post 577926) Thanks for response. This is for my daughter, can you explain like my example if possible please. like 3 times 3 = 9 minus 1 = 8 Can you tell me what the answer is for -1? Thanks.
3 times -1 minus 1 =

-3 minus 1 =

-4

 abdul hadi harun September 13th, 2017 09:53 AM

given f(x) = 2x - 6, determine value of k if inverse function f(2k) = f(k+1).

 skipjack September 13th, 2017 12:35 PM

The function f(x) = 2x - 6 has inverse g(x) = x/2 + 3.
As g(2k) = k + 3 and f(k+1) = 2k + 2 - 6 = 2k - 4, these are equal for k = 7.

 sagar233 September 13th, 2017 11:55 PM

Quote:
 Originally Posted by jl1974 (Post 577923) Hi, Need help with the following please: equation is Y=3x -1 I have two rows X and Y and trying to work the answers for the Y coordinate, struggling when I get to the minus figures. X -3 -2 -1 0 1 2 3 Y ? ? ? -1 2 5 8 What are the (Y) answers for -1, -2 and -3 To get the first answer 8, I done 3x3-1 =8 and 3x2-1 = 5 Many thanks
Quote:
 Originally Posted by jl1974 (Post 577926) Thanks for response. This is for my daughter, can you explain like my example if possible please. like 3 times 3 = 9 minus 1 = 8 Can you tell me what the answer is for -1? Thanks.
$\displaystyle y=3x-1$

So,
If, $\displaystyle x=3$
Then, $\displaystyle y=3\times3-1=9-1=8$

$\displaystyle x=2$
Then, $\displaystyle y=3\times2-1=6-1=5$

$\displaystyle x=1$
Then, $\displaystyle y=3\times1-1=3-1=2$

$\displaystyle x=0$
Then, $\displaystyle y=3\times0-1=0-1=-1$

$\displaystyle x=-1$
Then, $\displaystyle y=3\times{-1}-1=-3-1=-4$

$\displaystyle x=-2$
Then, $\displaystyle y=3\times{-2}-1=-6-1=-7$

$\displaystyle x=-3$
Then, $\displaystyle y=3\times{-3}-1=-9-1=-10$

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