SOLUTION: Solve the solution 7x-8y=24 and xy^2=1 I've done the following so far x=1/y^2 substitute so...7(1/y^2)-8y=24 7=24y^2+8y^3 let t=y^2...7=24t+8t^2......did I

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Question 144312: Solve the solution 7x-8y=24 and xy^2=1
I've done the following so far x=1/y^2
substitute so...7(1/y^2)-8y=24
7=24y^2+8y^3
let t=y^2...7=24t+8t^2......did I do this correctly?
8(t^2 +3t)=7
8(t^2+3t+9/4)=7+18 complete the square
8(t+3/2)^2=25...if I have done this correctly, then what are my next steps...
Answer by vleith(2983) (Show Source):
You can put this solution on YOUR website!
7=24y^2+8y^3
let t=y^2...7=24t+8t^2......did I do this correctly?
No. Close but no cigar
let t=y^2...7=24t+8t^2. if you put y^2 back in to t, you get 7=24y^2+8y^4.
0 = 8y^3 + 24y^2 -7
Try this ? --> http://www.1728.com/cubic2.htm
http://www.1728.com/cubic.htm
Not pretty.