數學一問~! help

1. 7(5x+2)
= 35x + 14----使用分配律

2. 3(2x+3)
= 6x + 9----使用分配律

3. 4(3x-5)
= 12x - 20----使用分配律

4. (2x+3y)(5x-2y)
= 10x^2 - 4xy + 15xy - 6y^2---------把2x分別乘5x和-2y、把3y分別乘5x和-2y
= 10x^2 + 11xy - 6y^2(合併同類項)

5. (7x-2)(-x+3)
= -7x^2 + 21x + 2x - 6---------把7x分別乘-x和3、把-2分別乘-x和3
= -7x^2 + 23x - 6(合併同類項)

***如果第5題怕負號的話,可以把題目的-x+3轉為3-x

6. (x+2y)(3x-y)
= 3x^2 - xy + 6xy - 2y^2---------把x分別乘3x和-y、把2y分別乘3x和-y
= 3x^2 + 5xy - 2y^2(合併同類項)

***我諗最尾果3題最大機會考試出
希望你能早日掌握

1. 35x+14
2. 6x+9
3. 12x-20
4.

1)35x+14
2)6x+9
3)12x-20
4)10xx-4xy+15xy-6yy
5)-7xx+21x-(-2x)-(-6)
6)3xx-xy+6xy-2yy

1) 7(5x+2)
=7*5x+7*2
=35x+14

2) 3(2x+3)
=3*2x+3*3
=6x+9

3) 4(3x-5)
=4*3x-5*4
=12x-20

4) (2x+3y)(5x-2y)
=2x*5x-2x*2y+3y*5x-3y*2y
=10x^2-4xy+15xy-6y^2

5) (7x-2)(-x+3)
=-x*7x+3*7x+2*x-3*2
=-7x^2-6+21x-6x

6) (x+2y)(3x-y)
=x*3x-x*y+2y*3x-2y*y
=3x^2-xy+6xy-2y^2

1)
35x+14
2)
6x+9
3)
12x-20
4)
10x^2 +4xy - 6y^2
5)
-7x^2 + 23x -6
6)
3x^2 +5xy - 2y^2

1)
7(5x+2)=35x+14
2)
3(2x+3)=6x+9

3)
4(3x-5)=12x-20
4)
(2x+3y)(5x-2y)
=10x^2+11xy-6y^2

5)
(7x-2)(-x+3)
=-7x^2+23x-6

6)
(x+2y)(3x-y)
=3x^2+5xy-2y^2