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Factorise the following expressions (i) 7𝑥 – 42 (ii) 6𝑝 − 12𝑞 (iii) 7𝑎2 + 14𝑎 (iv) −16𝑧 + 20𝑧3About 1 year ago

Subject : Mathematics Class : Class 8

Posted By :

Venkatesh

i) 7x - 42, 7x = 7*x

42 = 2 * 3 * 7, so the common factor is 7.

so 7x - 42 = 7*x - 2 * 3 * 7 = 7 ( x - 6)

ii) 6p = 2 * 3 * p

12 q = 2 * 2 * 3 * q, so the common factors are 2 * 3
so 6p - 12q = (2 * 3 * p) - ( 2 * 2 * 3 * q) = 2 * 3 [p - (2 * q)] = 6 (p - 2q)

iii) 7a^2 = 7 * a * a
14a = 2 * 7 * a, the common factors are 7 and a.
So 7a^2 14a = (7 * a * a) (2 * 7 * a) = 7 * a[a 2] = 7a( a 2)

iv) 16𝑧 = 2 * 2 * 2 * 2 * z
20z^3 = 2 * 2 * 5 * z * z * z
Common factor are 2, 2, and z.
so -16z 20z^3 = - (2 * 2 * 2 * z) (2 * 2 * 5 * z * z * z) = (2 * 2 * z) [- (2 * 2) (5 * z * z)] = 4z (- 4 5z^2)