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Maths gcse urgent help.

Solve the equation:
6/y^2 + 5/y -4 = 0
I am cross multiplying so I am getting 6y+5y^2 all divided by y^3 = 4
My method seems incorrect and I am not sure why.
All you need to do is cross-multiply to get 5y^2 + 6y -24/(y^3-4y^2) = 0
Then times both sides by (y^3-4y^2), to give 5y^2 + 6y -24=0 as anything times 0 is 0.
Then you use the quadratic formula to get x=1.67 and one more solution, which I'll leave you to figure out, rather than give you the entire answer :smile: Hope this helps
Original post by Wolfram Alpha
Solve the equation:
6/y^2 + 5/y -4 = 0
I am cross multiplying so I am getting 6y+5y^2 all divided by y^3 = 4
My method seems incorrect and I am not sure why.

see above
Original post by 1jonam16
All you need to do is cross-multiply to get 5y^2 + 6y -24/(y^3-4y^2) = 0
Then times both sides by (y^3-4y^2), to give 5y^2 + 6y -24=0 as anything times 0 is 0.
Then you use the quadratic formula to get x=1.67 and one more solution, which I'll leave you to figure out, rather than give you the entire answer :smile: Hope this helps


I don't quite understand where the -24/(y^3-4y^2) came from...
Original post by Wolfram Alpha
I don't quite understand where the -24/(y^3-4y^2) came from...


You need to cross multiply to get 6(y-4) + 5(y^2). This equals 6y -24 + 5y^2. Also as you cross multiplied, you need to multiply the denominators too. So (y^2)*(y-4)= y^3-4y^2. So you end up with 6y -24 + 5y^2 / y^3-4y^2.
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Avatar for Oinkpig3
Oinkpig3
Aren't the two answers y=-4/3 and y=1/2 ? What do you mean by cross multiplying?

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