(1) x2+(3a+4b)x+(2a2+5ab+3b2)
= x2+3ax+4bx+2a2+5ab+3b2)
= x2+ax+bx+2a2+2ax+2ab+3b2+3bx+3ab
= x2+ax+bx+2ax+2a2+2ab+3bx+3ab+3b2
= x(x+a+b) + 2a(x+a+b)+ 3b(x+a+b)
= (x+a+b)(x+2a+3b)
(2) (x2-x)2+3(x2-x)-40
= (x2-x)2+8(x2-x)-5(x2-x)-40
= (x2-x)(x2-x+8)-5(x2-x+8)
= (x2-x-5)(x2-x+8)
(3) 15x2-11xy-12y2
= 15x2-20xy+9xy-12y2
= 5x(3x-4y)+3y(3x-4y)
= (5x+3y)(3x-4y)
*** না বুঝলে মন্তব্য করুন।