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Grade 8 - Mathematics
7.44 Problems - VIII

Example:
If a-b = 3 and ab = 10, find the value of a3-b3.
Solution:
Given that,
a-b = 3
Cubing on both sides, we get
(a-b)3 = 33
a3-b3-3ab(a-b) = 27
a3-b3-3.10.3 = 27
a3-b3-90 = 27
a3-b3 = 27 + 90
a3-b3 = 117


Directions: Solve the following problems. Also write at least ten examples of your own.
Q 1: If a-b = 3 and ab = 18, find the value of a3-b3.
187
185
189
183

Q 2: If a-b = 4 and ab = 21, find the value of a3-b3.
316
318
314
312

Q 3: If a-b = 6 and ab = 16, find the value of a3-b3.
528
524
520
526

Q 4: If a-b = 10 and ab = 75, find the value of a3-b3.
3250
3255
3240
3245

Q 5: If a-b = 6 and ab = 91, find the value of a3-b3.
1852
1854
1858
1856

Q 6: If a-b = 8 and ab = 48, find the value of a3-b3.
1668
1664
1662
1666

Question 7: This question is available to subscribers only!

Question 8: This question is available to subscribers only!


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