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# Maths question that i can't do D: watch

1. Sorry if this is reaaaaaaally easy but my mind's just gone blank so yeah. XD

I'm stuck on this question about solving simultaneous equations with substituition...

x² + y² = 64
y = 2x + 8

What i've done so far is:

x² + (2x + 8)² = 64
x² + (2x + 8)(2x + 8) = 64

(2x + 8)(2x + 8) = 4x² + 16x + 16x + 64 = 64

so

x² + 4x² + 32x + 64 = 64
5x² + 32x + 0 = 0

Now I'm stuck. How do I get that into brackets so i can work out x? D:
2. You can factorise out the x. So you have

x(5x+32)=0

So either x=0 or 5x+32=0.

Can you do it now?

3. or
4. If you don't immediately see anything, you can always use the quadratic formula

I'll put it below just for your convenience

By the way, if you're not sure what this is, then you probably haven't done this yet.
In this case, thomaskurian89's post would probably be more for you
5. (Original post by 0-))
You can factorise out the x. So you have

x(5x+32)=0

So either x=0 or 5x+32=0.

Can you do it now?
Omg im such an idiot, ty for help!!
In the end i got y = 8 or y = -4.8
6. (Original post by placenta medicae talpae)
If you don't immediately see anything, you can always use the quadratic formula

I'll put it below just for your convenience

By the way, if you're not sure what this is, then you probably haven't done this yet.
In this case, thomaskurian89's post would probably be more for you
Oh yeah. I forgot about that. Thanks for help, i'll try using it now
7. (Original post by Aileena)
Oh yeah. I forgot about that. Thanks for help, i'll try using it now
No worries
Did you get the same answers out?!

I don't know about you, but I think it's good to have a method that always works, even if there are other "short cut" methods in certain circumstances.
8. All I can do is to say thank you

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9. (Original post by placenta medicae talpae)
No worries
Did you get the same answers out?!

I don't know about you, but I think it's good to have a method that always works, even if there are other "short cut" methods in certain circumstances.
Yes I did, thank you

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