中二數學一問(2)

1.(2x+4)(3x)
= 6x2+12x

2.(-9x)(11x2+2)
= -99x3 - 18x

3.(x - 4)(x+5)
= x2+5x - 4x - 20
= x2+x - 20

4.(3x+4)(4x-3)
= 12x2 - 9x+16x - 12
= 12x2+7x - 12

5.(-x-y)(-y-x)
= xy+x2+y2+xy
= x2+2xy+y2

6.(2x2 - x+3)(3x-2)
= 6x3 - 3x2 +9x - 4x2+2x - 6
= 6x3 - 7x2 +11x - 6

7.(4x2+5)(1 - 2x)
= 4x2 - 8x3 +5 - 10x
= - 8x3 +4x2 - 10x+5

8.(4a2 - 2ab+b2)(-2a-b)
= -8a3+4a2b - 2ab2 - 4a2b+2ab2 - b3
= -8a3 - b3

9.它的面積
= (4x2-x+3)(x+1)
= 4x3 - x2+3x+4x2- x+3
= 4x3+3x2+2x+3

10.(2x - 3)2
= 4x2 - 12x+9

1.(2x+4)(3x)
=(2x)(3x)+(4)(3x)
=6x^2+12x

2.(-9x)(11x^2+2)
=-99x^3-18x

3.(x-4)(x+5)
=x^2-4x+5x-20
=x^2+x-20

4.(3x+4)(4x-3)
=12x^2+16x-9x-12
=12x^2+7x-12

5.(-x-y)(-y-x)
=xy+y^2+x^2+xy
=xy^2+y^2+x^2

6.(2x^2-x+3)(3x-2)
=6x^3-3x^2+9x-4x^2+2x-6
=6x^3-7x^2+11x-6

7.(4x^2+5)(1-2x)
=4x^2+5-8x^3-10x
=8x^3+4x^2-10x+5

8.(4a^2-2ab+b^2)(-2a-b)
=-8a^3+4a^2b-b^3

9.(4x^2-x+3)(x+1)
=4x^3-x^2+3x+4x^2-x+3
=4x^3+3x^2+2x+3

10.(2x-3)^2
=4x^2-9

註:^ = 次方 , e.g : ^2=2次方 , ^3=3次方...

1. (2x+4)(3x)
=3x(2x)+3x(4)
=6x二次+12x
=6x(x+2)

2.(-9x)(11x二次+2)
=-9x(11x二次)+(-9x)(2)
=-99x三次-18x
=-9x(11x二次+2)

3.(x-4)(x+5)
=x(x+5)-4(x+5)
=x二次+5x-4x-5
=x二次+x-5

4.(3x+4)(4x-3)
=3x(4x-3)+4(4x-3)
=12x二次-9x+16x-12
=12x二次+7x-12

5.(-x-y)(-y-x)
=(-x-y)(-x-y)
=(-x-y)二次
=(-x)二次-2xy+(-y)二次
=x二次-2xy+y二次

6.(2x二次-x+3)(3x-2)
=3x(2x二次-x+3)-2(2x二次-x+3)
=6x二次-3x二次+9x-4x二次+2x-6
=-x二次+11x-6
=11x-x二次-6

7.(4x二次+5)(1-2x)
=1(4x二次+5)-2x(4x二次+5)
=4x二次+5-8x二次-10x
=-4x二次-10x+5

8.(4a二次-2ab+b二次)(-2a-b)
=-2a(4a二次-2ab+b二次)-b(4a二次-2ab+b二次)
=-8a三次+4ba二次-2ab二次-4ba二次+2ab二次-b三次
=-(8a三次+b三次)
(f.3的話,仲未計完,不過我唔知你間學校嘅程度,所以計埋比你)
=-((2a)三次+b三次)
=-(2a+b)((2a二次)-(2a)(b)+b二次)
=-(2a+b)(4a二次-2ab+b二次)

9.長方形的長和闊分別是,求它的面積。
長方形的面積
=(4x二次-x+3)(x+1)
=x(4x二次-x+3)+1(4x二次-x+3)
=4x三次-x二次+3x+4x二次-x+3
=4x三次+3x二次+6

10.(2x-3)二次
=(2x)二次 -2(2x)(3)+3二次
=4x二次-12x+3二次

1. 6x^2+12x
2. -1107x
3. x^2+x-20
4. 12x^2+7x-12
5. x^2+y^2
6. -3x^2+23x-14
7. 9-18x
8. 21-42x
9. 19x=18-x^2
10. 4x^2-12x+9