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# Why does he do this? - GCSE maths watch

1. http://www.mrbartonmaths.com/resourc...0Solutions.pdf

Question 22 ( b )

Why does it become 2/y^2 + 9y/y^2 - 7y/y^2 = 0
-7y^2 + 9y + 2 = 0
??

Thanks, would appreciate if you could tell me why he does this, as I'm stuck.

Also, if you're feeling very helpful, on Q19 why does it go from 8 x 10^8 to 8 x 10^11 in the workings?

Thanks!
2. (Original post by iMacJack)
http://www.mrbartonmaths.com/resourc...0Solutions.pdf

Question 22 ( b )

Why does it become 2/y^2 + 9y/y^2 - 7y/y^2 = 0
-7y^2 + 9y + 2 = 0
??

Thanks, would appreciate if you could tell me why he does this, as I'm stuck.

Also, if you're feeling very helpful, on Q19 why does it go from 8 x 10^8 to 8 x 10^11 in the workings?

Thanks!
22b. He multiplies each term by to get all positive powers of y. The equation is then easy to solve-it's a quadratic.

19. There's a general rule for multiplying indices: . So .
3. I think on the first one it is because the three y^2 cancel out, as they are all in the denominator, although I'd ask for confirmation of that.

4. Hi, thanks but for no. 19 where did he get the extra 3 powers from I understand the rules of indices but where did he get the extra 8 x 10^3 from
5. (Original post by iMacJack)
Hi, thanks but for no. 19 where did he get the extra 3 powers from I understand the rules of indices but where did he get the extra 8 x 10^3 from
The distance between Jupiter and the Sun is given in km. The converts it to metres to compare with the other distance, which is given in metres.

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