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zara:
Find the real roots of the equation 18/x4 + 1/x2 =4

can summon plz explain?
                                          

astarmathsandphysics:
Start by multiplying by x4. Home in 4 hours.

slvri:
18/x4 + 1/x2 =4
multiply by x4
18+x2=4x4
4x4-x2-18=0
4(x2)2-x2-18=0
u can see that this is a quadratic equation in x2
factorising we have
4x4-9x2+8x2-18=0
x2(4x2-9)+2(4x2-9)=0
(4x2-9)(x2+2)=0
either 4x2-9=0 or x2+2=0
4x2=9 or x2=-2
x2=9/4 (x2=-2 has no real roots, complex roots are +-sqrt(2)i)
so from the first one
x=sqrt(9/4)
x=+-(3/2)
hope this helped zara :)

nid404:
 zara slvri has done it for ya and it's right....Thanks slvri :)

zara:
18/x4 + 1/x2 =4
multiply by x4
18+x2=4x4
4x4-x2-18=0
4(x2)2-x2-18=0
u can see that this is a quadratic equation in x2
factorising we have
4x4-9x2+8x2-18=0
x2(4x2-9)+2(4x2-9)=0
4(x2-9)(x2+2)=0
either 4x2-9=0 or x2+2=0
4x2=9 or x2=-2
x2=9/4 (x2=-2 has no real roots, complex roots are +-sqrt(2)i)
so from the first one
x=sqrt(9/4)
x=+-(3/2)





the ones in red i didnt get it....plz elaborate... :-\
y is 4x2-9=0? wont it be x2-9=0?

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