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 August 17th, 2017, 12:26 PM #1 Newbie   Joined: Aug 2017 From: glasgow Posts: 2 Thanks: 0 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 Last edited by jl1974; August 17th, 2017 at 12:28 PM.
August 17th, 2017, 12:34 PM   #2
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Quote:
 Originally Posted by jl1974 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 $x=-2,~-3$

 August 17th, 2017, 12:48 PM #3 Newbie   Joined: Aug 2017 From: glasgow Posts: 2 Thanks: 0 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. Last edited by jl1974; August 17th, 2017 at 01:08 PM.
August 17th, 2017, 02:47 PM   #4
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Quote:
 Originally Posted by jl1974 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.

August 17th, 2017, 04:00 PM   #5
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Quote:
 Originally Posted by jl1974 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

 September 13th, 2017, 09:53 AM #6 Newbie   Joined: Sep 2017 From: malaysia Posts: 1 Thanks: 0 Hi everyone, please help me to solve this equation, my brain stuck already... given f(x) = 2x - 6, determine value of k if inverse function f(2k) = f(k+1). Please help me with the detailed solution. Last edited by skipjack; September 13th, 2017 at 12:30 PM.
 September 13th, 2017, 12:35 PM #7 Global Moderator   Joined: Dec 2006 Posts: 19,295 Thanks: 1686 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. Thanks from abdul hadi harun
September 13th, 2017, 11:55 PM   #8
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Quote:
 Originally Posted by jl1974 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 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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