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Grade 8 - Mathematics
7.14 Solving Problems Using Formula for (a+b)2

Example: If (x+1/x) = 6 find x2+1/x2.
Solution: Given that (x+1/x) = 6 .
Take square on both sides.
(x+1/x)2 = 62
x2 + 2.x.1/x + (1/x)2  = 36
x2 + (1/x)2 = 36-2
x2 + (1/x)2 = 34

Directions: Solve the following problems. Also write at least ten examples of your own.
Q 1: If (x+1/x) = 5 find x2+1/x2.
25
27
23

Q 2: If (x+1/x) = 9 find x2+1/x2.
99
89
79

Q 3: If (x+1/x) = 11 find x2+1/x2.
115
119
121

Q 4: If (x+1/x) = 15 find x2+1/x2.
225
216
223

Q 5: If (x+1/x) = 20 find x2+1/x2.
450
398
402

Q 6: If (x+1/x) = 25 find x2+1/x2.
625
630
623

Q 7: If (x+1/x) = 4 find x2+1/x2.
14
26
16

Q 8: If (x+1/x) = 3 find x2+1/x2.
5
7
9

Question 9: This question is available to subscribers only!

Question 10: This question is available to subscribers only!


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