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I am given equations for straight lines. Some are in the form y=mx+c (or y=mx+b as it might be in your part of the world). I need to put them in that form if possible because I am asked to find the gradient and y-intercept of them.

One of the straight lines is: 2y=6x-7 I know that I have to get the y by itself so I need to divide the 2y, 6x and -7 by two. I ended up with: y=3x-7/2
When showing how I got my answer do I keep the y-intercept as a fraction? When asked for the y-intercept do I give it as 7/2 or as 3.5? I would have thought as a decimal. Please help!

Also if the straight line is: y=4 Is the gradient 0 and the y-intercept 4? I'm pretty certain it is but I'm just making sure. Thanks for helping.

Also, If the straight line is x=-8 and I'm asked for the gradient and y-intercept is the answer 0 to both of them (gradient and y-intercept)? Thanks!

2007-02-21 20:03:15 · 5 answers · asked by Anonymous in Science & Mathematics Mathematics

I have another one where the y-intercept = 1/7. If I put it into decimal form it won't be the proper number (it will be an approximation). What do I do? Decimals or fractions for gradients and y-intercepts?

2007-02-21 20:15:12 · update #1

Do you think I'll get them wrong if I give them as fractions or improper fractions rather than decimals and mixed numbers? Would I be better of expressing them as fractions as well as mixed numbers rather than also improper fractions such as -7/2 would I be better of giving the y-intercept as 3 1/2?

2007-02-21 20:26:42 · update #2

5 answers

For your 1st qns,
When asked for the y-intercept do I give it as 7/2 or as 3.5?
I think it doesn't matter if you give your answer as a fraction or a a decimal unless the qns states explicitly if it requires a fraction or decimal form.

Also if the straight line is: y=4 Is the gradient 0 and the y-intercept 4?
Yes, you are right. The gradient is zero because this is a horizontal line. If you have learnt trigo, the gradient can be found by tan x, where x is the anticlockwise angle measured from the horizontal (x axis).

Hence, for your 3rd qns, Also, If the straight line is x=-8 and I'm asked for the gradient and y-intercept is the answer 0 to both of them (gradient and y-intercept)?

The gradient is infinity as this is a vertical line and also tan 90 is infinity. Perhaps the y intercept would be undefined instead of 0 cause y intercept of 0 may mean that the line cuts the x axis, where y=0 at all pts on the x axis.

Hope this clarifies your doubts. =)

2007-02-21 20:15:43 · answer #1 · answered by tabletennisrulez 2 · 0 0

Question 1
2y = 6x - 7
y = 3x - 7/2 is correct.
Cuts y axis at (0 , 7/2) is also correct as is (0 , 3.5)

Question 2
y = 4 is a horizontal line that passes thro` (0 , 4)
Gradient = 0 ie it is not "rising" or "falling".


Question 3
x = - 8 is a vertical line that passes thro` (-8 , 0)
This line does not cut the y axis so there is no y intercept.
The x intercept is (- 8, 0)
Gradient of vertical line is ∞

2007-02-21 20:53:50 · answer #2 · answered by Como 7 · 0 0

You are definatly on the right track. It is an issue of style for expressing fractions. Ask your instructor the preferred style for class.
Unfortunatly the gradient intercept method does not handle the x=8 case.

2007-02-21 20:20:04 · answer #3 · answered by Roy E 4 · 0 0

1. The y-intercept would be -7/2.

2. correct: gradient(slope) = 0, y-intercept = 4

3. the gradient(slope) of a vertical line is not 0, it is defined as having no slope, not 0 slope. there is no y-intercept for a x=-8 line.

2007-02-21 20:14:00 · answer #4 · answered by dka2012 4 · 0 0

Honey it is too late to be doin Homework........Goodluck on finding your answer though....

2007-02-21 20:12:23 · answer #5 · answered by blackandlovely06 1 · 0 0

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