Ex 12.1, 2 (Method 1) Factorise the following expressions. (iv) – 16z + 20 𝑧^3− 16z + 20𝑧^3
= (4 × −4) z + (4 × 5)𝑧^3
Taking 4 common,
= 4 (−4z + 5𝑧^3)
= 4 (−4 × z + 5𝑧^2 × z)
Taking z common,
= 4 × z (−4 + 5𝑧^2)
= 4z (−4 + 5𝒛^𝟐)
Ex 12.1, 2 (Method 2) Factorise the following expressions. (iv) – 16z + 20 𝑧^3−16z = −16 × z
= −1 × 16 × z
= −1 × 2 × 2 × 2 × 2 × z
20𝒛^𝟑 = 20 × 𝑧^3
= 2 × 2 × 5 × z × z × z
So, 2, 2 and z are the common factors.
Now
−16z +20𝑧^3
= (−1 × 2 × 2 × 2 × z) + (2 × 2 × 5 × z × z × z)
Talking 2 × 2 × z common,
= 2 × 2 × z ((−1 × 2 × 2) + (5 × z × z))
= 4z (−4 + 5𝒛^𝟐)
Made by
Davneet Singh
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
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