C1 Question

Youngey4

How would I answer question 4? I think I have the answer to a)

(edited 7 years ago)

20161025_205412.jpg517.8KB

Reply 1

NotNotBatman

So, you have;

x^{\frac{3}{2}} - \frac{8}{x^\frac{1}{2}}=0

I would start by multiplying both sides by

x^\frac{1}{2}

Reply 2

Youngey4

Original post by NotNotBatman

So, you have;

x^{\frac{3}{2}} - \frac{8}{x^\frac{1}{2}}=0

I would start by multiplying both sides by

x^\frac{1}{2}

Oh so you'd get x^4/2 -8 = 0
which would be x^2 - 8 =0
x^2 = 8
x = sqrt(8)
x = 2 x sqrt(2)
Thanks so much

Reply 3

Youngey4

Original post by NotNotBatman

No. On the first term

x^{\frac{3}{2}} \times x^{\frac{1}{2}} = x^{\frac{3}{2} \times \frac{1}{2}} =x^{\frac{3}{4}}

But in the laws of indices, don't you add the indices when multiplying terms?

Reply 4

NotNotBatman

Original post by Youngey4

But in the laws of indices, don't you add the indices when multiplying terms?

Oh yeah, I made a mistake, you've got it right, I'll delete the post.

Reply 5

Youngey4

Original post by NotNotBatman

Oh yeah, I made a mistake, you've got it right, I'll delete the post.

No worries, thanks for the initial help :smile:

Reply 6

B_9710

I wonder why the questions asks for answers.
Maybe it's to trick people.

Reply 7

aoxa

Original post by B_9710

I wonder why the questions asks for answers.
Maybe it's to trick people.

Or both the positive and negative square root?

Reply 8

Youngey4

Original post by aoxa

Or both the positive and negative square root?

Yeah thats what I put, the plus or minus answer.

Reply 9

NotNotBatman

Original post by Youngey4

Yeah thats what I put, the plus or minus answer.

So substituting back into the original what is

(-2\sqrt{2})^\frac{3}{2}

? You'll find that there isn't a real solution.

Reply 10

B_9710

Original post by aoxa

Or both the positive and negative square root?

In the original equation it doesn't work. Graph the original function and you'll see.

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