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Grade 8 - Mathematics
7.45 Problems - IX

Example:
If x+1/x = 3, find the value of x3+1/x3.
Solution:
Given that,
x+1/x = 3
Cubing on both sides, we get
(x+1/x)3 = 33
x3+1/x3+3.x.1/x.(x+1/x) = 27
x3+1/x3+3.3 = 27
x3+1/x3+9 = 27
x3+1/x3 = 27-9
x3+1/x3 = 18


Directions: Solve the following problems.
Q 1: If x+1/x = 5, find the value of x3+1/x3.
113
119
115
117

Q 2: If x+1/x = 2, find the value of x3+1/x3.
4
6
2
8

Q 3: If x+1/x = 6, find the value of x3+1/x3.
192
196
198
194

Q 4: If x+1/x = 10, find the value of x3+1/x3.
970
960
965
975

Q 5: If x+1/x = 8, find the value of x3+1/x3.
484
482
486
488

Q 6: If x+1/x = 4, find the value of x3+1/x3.
52
56
58
54

Question 7: This question is available to subscribers only!

Question 8: This question is available to subscribers only!


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