計數: factorization (因式分解)

18p^2 - 2q^2 + 12q - 18

= 2 ( 9p^2 - q^2 + 6q - 9) ..................[9 = 3x3] [6q = 2x3xq]

= 2 ( 3^2xp^2 - (q^2 - 2(3)(q) + 3^2) ) [a^2 x b^2 = (ab)^2]
................................................. . [a^2 - 2ab + b^2 = (a-b)^2]

= 2 ( (3p)^2 - (q-3)^2 ) ...................[a^2 - b^2 = (a-b) x (a+b)]

= 2 ( 3p - (q-3) ) ( 3p + (q-3) )

= 2 (3p-q+3) (3p+q-3) //


Hope these can help you !!
Cheers! :)

18p^2-2q^2+12q-18
2(9p^2-q^2+6q-9)
2((3p)^2-(q-3)^2)
2(3p-q+3)(3p+q-3)