Question

plzz answer this question tomorrow is my exam

Answer 1

x^4 +1/x^4 = 47

add 2(x^2 *1/x^2 ) on both sides,

x^4 +1/x^4 +2 = 47+2

x^4 +1/x^4 +2 = 49

it will convert into (x^2+1/x^2)^2 = 49  by the formula (a+b)^2

then, (x^2 +1/x^2)^2 = 49

x^2 + 1/x^2 = 7

again add 2(x*1/x) on both sides,


x^2 +1/x^2 + 2 = 7+2

(x+1/x)^2 =9

(x+1/x)= 3


now, 

(x+1/x) = 3

then, cube on both sides ,

(x+1/x)^3 = 3^3

x^3 +1/x^3 +3(x*1x) {x+1/x} = 27

x^3 +1/x^3 +(3*3) = 27

x^3 +1/x^3 = 27-9

x^3 +1/x^3 = 18



i hope this will help you 




- by ABHAY