不明白這幾題數(簡易方程式)

5(a+b-2c)=5a+5b-10c
(a^2 - 3b ) (2a)=2a^3-2a3b

14x-21= 7(2x-3)
3p + 5pq=p(3+5q)


(x+1)(x+4)= x^2+x+4x+4=x^2+5x+4
(2x-1)(x+5)=2x^2-x+10x-5=2x^2+9x--5
(3n+2)^2=(3n+2)(3n+2)=let a=3n b=2
=a^2+2ab+b^2= 9n^2+12n+4
(2n - 10)^2= a^2-2ab+b^2=4n^2--40n+100

(k-3)(k+3)=k^2-3k+3k-9=k^2-9

(3-4y)(4y+3)=12y-16y^2+9-12y=9-16y^2

展開下列各式
5(a+b-2c)
=5a+5b-10c

(a^2 - 3b ) (2a)
=2a^3 -6ab

用提取公因式的方法,把下列多項式分解為因式

14x-21
=7(2x-3)

3p + 5pq
=p(3+5q)

展開下列各式

(x+1)(x+4)
=x^2+5x+4

(2x-1)(x+5)
=2x^2+9x-5

(3n+2)^2
=9n^2+12n+4

(2n - 10)^2
=4n^2-40n+100

(k-3)(k+3)
=k^2-9

(3-4y)(4y+3)
=9-16y^2