Example 20 - Chapter 2 Class 9 Polynomials

Last updated at April 16, 2024 by

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Example 20 Factorise : 8x3 + y3 + 27z3 – 18xyz 8x3 + y3 + 27z3 – 18xyz = (2x) 3 + y3 + (3z) 3 – 18xyz = (2x) 3 + y3 + (3z) 3 – 3(2x)(y)(3z) Using a3 + b3 + c3 – 3abc = (a + b + c)(a2 + b2 + c2 – ab – bc – ca) Putting a = 2x, b = y , c = 3z = (2x + y + 3z)[(2x)2 + y2 + (3z) 2 – (2x)(y) – (y)(3z) – (2x)(3z)] = (2x + y + 3z) (4x2 + y2 + 9z2 – 2xy – 3yz – 6xz)

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Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo