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Important Questions

Identities — Important Questions

ICSE · Class 8 · Mathematics

75 important questions from Identities for ICSE Class 8 Mathematics, with answers. Includes multiple choice, true false and multiple correct questions.

75 questions28 flashcards7 formulas & key relations5 concepts

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75 Questions·
multiple choicetrue falsemultiple correct

Important Questions from Identities

1multiple choice
3 marks

If a + b = 8 and ab = 15, find a^2 + b^2.

Show answer

34

Use (a + b)^2 = a^2 + b^2 + 2ab. Given a + b = 8 and ab = 15. 8^2 = a^2 + b^2 + 2×15 64 = a^2 + b^2 + 30 So, a^2 + b^2 = 64 - 30 = 34.

2multiple choice
3 marks

If a - b = 3 and a^2 + b^2 = 29, find ab.

Show answer

10

Use (a - b)^2 = a^2 + b^2 - 2ab. Given a - b = 3 and a^2 + b^2 = 29. 3^2 = 29 - 2ab 9 = 29 - 2ab 2ab = 20 ab = 10.

3multiple choice
3 marks

If a + b + c = 9 and a^2 + b^2 + c^2 = 29, find ab + bc + ca.

Show answer

26

Use (a + b + c)^2 = a^2 + b^2 + c^2 + 2(ab + bc + ca). Given a + b + c = 9 and a^2 + b^2 + c^2 = 29. 9^2 = 29 + 2(ab + bc + ca) 81 = 29 + 2(ab + bc + ca) 52 = 2(ab + bc + ca) ab + bc + ca = 26.

4multiple choice
3 marks

If a + b = 5 and ab = 6, find a^3 + b^3.

Show answer

35

Use a^3 + b^3 = (a + b)^3 - 3ab(a + b). Given a + b = 5 and ab = 6. So, a^3 + b^3 = 5^3 - 3×6×5 = 125 - 90 = 35.

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Frequently Asked Questions

What are the important topics in Identities for ICSE Class 8 Mathematics?
Key topics in Identities include Identity and Special Products, Expansion of Squares, Cubes of Binomials, Application of Identities. Study these first, then practise questions on each for Class 8 exams.
How many important questions are there in Identities?
Super Tutor has 75 practice questions for Identities, including multiple choice, true false, multiple correct questions. A sample with answers is on this page.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

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All ICSE Class 8 Mathematics Important Questions

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