中一數學..(問一題=.=)聽日交,10分!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

(ab+2b)(3a-1)

ab+2b
× 3a-1
--------------------------
3a^2b+6ab
-ab-2b
--------------------------
3a^2b+5ab-2b

(ab+2b)(3a-1)
=3a(ab+2b)-1(ab+2b)
=3(a)2次b+6ab-ab-2b
=3(a)2次b+5ab-2b




must right

(ab+2b)(3a-1)

=(a+3b)x(3a-1)

=3bx4a-1

all don't use 直式??!!

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(ab+2b)(3a-1)
=3a二次b-ab+6ab-2b
=3a二次b-ab+4a//

=3a^2+5ab-2b

b+5ab-2b

2
3a +5ab-2b

用唔用直式都一樣啦

3a2次b+5ab-2b