Question 475899
x4 -  7x2 + 6 = 0 

x^2=u

u^2-7u+6=0
u^2-6u-u+6=0
u(u-6)-1(u-6)=0
(u-6)(u-1)=0
u=6 OR 1

x^2= 6 OR x^2=1

x= +/-sqrt(6) 
OR
x= +/-(1)

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