Hello, there's a vector question I'm stuck on.

D, E and F are 3 points on a straight line such that

Vector DE = 3e + 6f

Vector EF = -10.5e - 21f

Find the ratio

Length of DF: length of DE

I get that if DE and EF are on the straight line, that DF = (3e + 6f) + (-10.5e - 21f), which is -7.5f -15f.

So -7.5f -15f : 3e + 6f

But I don't understand what to do next, can anyone help?

D, E and F are 3 points on a straight line such that

Vector DE = 3e + 6f

Vector EF = -10.5e - 21f

Find the ratio

Length of DF: length of DE

I get that if DE and EF are on the straight line, that DF = (3e + 6f) + (-10.5e - 21f), which is -7.5f -15f.

So -7.5f -15f : 3e + 6f

But I don't understand what to do next, can anyone help?

Original post by Bladerun2

Hello, there's a vector question I'm stuck on.

D, E and F are 3 points on a straight line such that

Vector DE = 3e + 6f

Vector EF = -10.5e - 21f

Find the ratio

Length of DF: length of DE

I get that if DE and EF are on the straight line, that DF = (3e + 6f) + (-10.5e - 21f), which is -7.5f -15f.

So -7.5f -15f : 3e + 6f

But I don't understand what to do next, can anyone help?

D, E and F are 3 points on a straight line such that

Vector DE = 3e + 6f

Vector EF = -10.5e - 21f

Find the ratio

Length of DF: length of DE

I get that if DE and EF are on the straight line, that DF = (3e + 6f) + (-10.5e - 21f), which is -7.5f -15f.

So -7.5f -15f : 3e + 6f

But I don't understand what to do next, can anyone help?

What do you notice about the ratios for each of the e and f coefficients?

It may help to just sketch a simple, exemplar line to get the right argument.

(edited 9 months ago)

Original post by mqb2766

What do you notice about the ratios for each of the e and f coefficients?

It may help to just sketch a simple, exemplar line to get the right argument.

It may help to just sketch a simple, exemplar line to get the right argument.

You have to times EF by -2.5 to get DE? So is the answer -2.5:1?

Original post by Bladerun2

You have to times EF by -2.5 to get DE? So is the answer -2.5:1?

Lengths are not negtive (its represents diretion) but otherwise thats correct.

You could say you had a basic vector

e+2f

one is 3 times that, the other is (-) 7.5 times that so 3:7.5 or 1:2.5 or 2:5 ratio (order may be swapped depending on what the quetion asked for).

(edited 9 months ago)

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