Factorise :
(i) 2a3−50a(ii)54a2b2−6(iii) 64a2b−144b3(iv) (2x−y)3−(2x−y)(v) x2−2xy+y2−z2(vi) x2−y2−2yz−z2(vii) 7a5−567a(viii) 5x2−20x49
(i) 2a3−50a=2a(a2−25)=2a(a2−52)=2a(a−5)(a+5)(ii)54a2b2−6=6(9a2b2−1)=6[(3ab)2−(1)2]=6(3ab−1)(3ab+1)(iii) 64a2b−144b3=16b(4a2−9b2)=16b[(2a)2−(3b)2]=16b(2a+3b)(2a−3b)(iv) (2x−y)3−(2x−y)=(2x−y)[(2x−y)2−1]=(2x−y)(2x−y−1)(2x−y+1)(v) x2−2xy+y2−z2=(x2−2xy+y2)−z2=(x−y)2−(z)2=(x−y−z)(x−y+z)(vi) x2−y2−2yz−z2=x2−(y2+2yz+z2)=x2−(y+z)2=(x−y−z)(x+y+z)(vii) 7a5−567a=7a(a4−81)=7a(a2)2−(9)2=7a(a2+9)(a2−9)=7a(a2+9)((a)2−(3)2)=7a(a2+9)(a+3)(a−3)(viii) 5x2−20x49=5x2[1−4x29]=5x2[1−2x3][1+2x3]