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Nice problem!I used Simon's Favourite Factoring Trick, multiplying through by 8 the cubic obtained by clearing denominators and isolating x, to obtain:(2x)³ = 8*x³ = 8*7√53 - 8*20 = 56√53 - 160 = 53√53 + 3*√53 - 3*53 - 1 = 53√53 - 3*53 + 3*√53 - 1 = (√53 - 1)³andx = ½ * (√53 - 1).Sometimes simpler is better.
X=(√53-1) /2x^3=7√53-20y^3=7√53+20x^3-y^3=-40, by formula (x-y) (x^2+xy+y^2) =-40t=x-yt^3+39t+40=0t=-1x-y=-1;x+y=±√53;solve them x=(√53-1) /2xy=13
χ=[(53)^(1/2)-1]/2
Where does the Y come from?
taking the conjugate of x^3
Nice problem!
I used Simon's Favourite Factoring Trick, multiplying through by 8 the cubic obtained by clearing denominators and isolating x, to obtain:
(2x)³ = 8*x³
= 8*7√53 - 8*20
= 56√53 - 160
= 53√53 + 3*√53 - 3*53 - 1
= 53√53 - 3*53 + 3*√53 - 1
= (√53 - 1)³
and
x = ½ * (√53 - 1).
Sometimes simpler is better.
X=(√53-1) /2
x^3=7√53-20
y^3=7√53+20
x^3-y^3=-40, by formula (x-y) (x^2+xy+y^2) =-40
t=x-y
t^3+39t+40=0
t=-1
x-y=-1;
x+y=±√53;solve them
x=(√53-1) /2
xy=13
χ=[(53)^(1/2)-1]/2
Where does the Y come from?
taking the conjugate of x^3