Why does he do this? - GCSE maths
http://www.mrbartonmaths.com/resources/GCSE%20Revision/Past%20Papers/9.%20November%202012/Nov%202012%20-%20Paper%202%20Higher%20-%20Written%20Solutions.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!
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!
Original post by iMacJack
http://www.mrbartonmaths.com/resources/GCSE%20Revision/Past%20Papers/9.%20November%202012/Nov%202012%20-%20Paper%202%20Higher%20-%20Written%20Solutions.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!
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 .
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. 
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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