Factorise the following expressions.
(i) `7x - 42`
(ii) `6p - 12q`
(iii) `7a^2 + 14a`
(iv) `-16z + 20z^3`
(v) `20l^2m + 30a l m`
(vi) `5x^2y - 15xy^2`
(vii) `10a^2 - 15b^2 + 20c^2`
(viii) `-4a^2 + 4ab - 4ca`
(ix) `x^2yz + xy^2z + xyz^2`
(x) `ax^2y + bxy^2 + cxyz`

Explanation

1)`7x-42=7(x-6)`

2)`6p-12q=6(p-2q)`

3)`7a^2+14a=7a(a+2)`

4)`-16z+20z^2=4z(5z-4)`

5)`20l^2m+30alm=10lm(2l+3a)`

6)`5x^2y-15xy^2=5xy(x-3y)`

7)`10a^2-15b^2+20c^2=5(2a^2-3b^2+4c^2)`

8)`-4a^2+4ab-4ca=4a(-a+b-c)`

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