Linear Graphs - Is my explanation correct?

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noodlestopshop
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I have the question "Write down the equation of the line that is parallel to y=6x + 1 and passes through (0,8)"

Then I have the options
y = 6x + 8
y = 6x -1
y = 3x + 1
y =3x -2
to work this out do I just put the x value (0) into each equation and find which one equals eight?
So, for the first one
y=6x+8 = y=6(0)+8 = y=8?
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Plücker
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(Original post by noodlestopshop)
I have the question "Write down the equation of the line that is parallel to y=6x + 1 and passes through (0,8)"

Then I have the options
y = 6x + 8
y = 6x -1
y = 3x + 1
y =3x -2
to work this out do I just put the x value (0) into each equation and find which one equals eight?
So, for the first one
y=6x+8 = y=6(0)+8 = y=8?
Yes but what if one of the other equations had been y=3x+8?
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hhqurashi
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(Original post by noodlestopshop)
I have the question "Write down the equation of the line that is parallel to y=6x + 1 and passes through (0,8)"

Then I have the options
y = 6x + 8
y = 6x -1
y = 3x + 1
y =3x -2
to work this out do I just put the x value (0) into each equation and find which one equals eight?
So, for the first one
y=6x+8 = y=6(0)+8 = y=8?
No, you have to use your knowledge of parallel lines. Parallel lines have the same gradient so we know that y=6x+c (where c is an unknown) as the six represents the gradient. Therefore we can already eliminate the last two options. Then sub in the point (0,8) to work out c.
So y=6x+c becomes 8=6(0)+c. Therefore c equals 8 so the final eq of the line is y=6x+8.
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noodlestopshop
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(Original post by hhqurashi)
No, you have to use your knowledge of parallel lines. Parallel lines have the same gradient so we know that y=6x+c (where c is an unknown) as the six represents the gradient. Therefore we can already eliminate the last two options. Then sub in the point (0,8) to work out c.
So y=6x+c becomes 8=6(0)+c. Therefore c equals 8 so the final eq of the line is y=6x+8.
Ohhhh, I didn't think about that, thankyou!
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noodlestopshop
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(Original post by Plücker)
Yes but what if one of the other equations had been y=3x+8?
That one would be incorrect because of the 3, it would need to be a 6 right?
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Plücker
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(Original post by noodlestopshop)
That one would be incorrect because of the 3, it would need to be a 6 right?
Right.
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hhqurashi
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(Original post by noodlestopshop)
Ohhhh, I didn't think about that, thankyou!
Np
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