數學問題..要過程...20分！！

x^2代表x的2次方

(1)
(x^2-2x)+(3-4x+x^2)
=x^2-2x+3-4x+x^3
=x^3+x^2-2x-4x+3
=x^3+x^2-6x+3

(2)
(5a+a^2+3)-(7+a+a^2)
=5a+a^2+3-7-a-a^2
=a^2-a^2+5a-a+3-7
=4a-4

(3)
-5x(x^2-2x+3)
=-5x(x^2)+(-5x)(-2x)+(-5x)(3)
=-5x^3+10x^2-15x

(4)
(-2m-3n)(4m-5n)
=-2m(4m-5n)-3n(4m-5n)
=-8m^2+10mn-12mn+15n^2
=-8m^2-2mn+15n^2

(5)
(-3b-2b^2+4)(5-b)
=5(-3b-2b^2+4)-b(-3b-2b^2+4)
=-15b-2b^2+20+3b^2+2b^3-4b
=2b^3-2b^2+3b^2-15b-4b+20
=2b^3+b^2-19b+20

(6)
2a(2a-7b)-2(3a^2-4ab+5)
=4a^2-14ab-6a^2+8ab-10
=4a^2-6a^2-14ab+8ab-10
=-a^2-6ab-10

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

2.(5a+a²+3)-(7-a+a²)
=5a + a² + 3 - 7 + a - a²
=a² - a² + 5a + a + 3 - 7
=6a - 4

3.-5x(x²-2x+3)
=-5x(x²) + (-5x)(-2x) + (-5x)(3)
=-5x³ + 10x² - 15x

4.(-2m-3n)(4m-5n)
=(-2m)(4m) + (-2m)(-5n) + (-3n)(4m) + (-3n)(-5n)
=-8m² + 10mn - 12mn + 15n²
=-8m² - 2mn + 15n²

5.(3b-2b²+4)(5-b)
=(3b)(5) + (-2b²)(5) + 4(5) + (3b)(-b) + (-2b²)(-b) + (4)(-b)
=15b - 10b² + 20 - 3b² + 2b³ - 4b
=2b³ - 10b² - 3b² + 15b - 4b + 20
=2b³ - 13b² + 11b + 20

6.2a(2a-7b)-2(3a²-4ab+5)
=[2a(2a) + 2a(-7b)] - [2(3a²) + 2(-4ab) + 2(5)]
=(4a² - 14ab) - (6a² - 8ab + 10)
=4a² - 14ab - 6a² + 8ab - 10
=4a² - 6a² - 14ab + 8ab - 10
=-2a² - 6ab - 10

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

2.(5a+a²+3)-(7-a+a²)
= 5a + a² + 3 - 7 + a - a²
=a² - a² + 5a + a + 3 - 7
= 6a - 4

3.-5x(x²-2x+3)
= -5x(x²) + (-5x)(-2x) + (-5x)(3)
= -5x³ + 10x² - 15x

4.(-2m-3n)(4m-5n)
=(-2m)(4m) + (-2m)(-5n) + (-3n)(4m) + (-3n)(-5n)
= -8m² + 10mn - 12mn + 15n²
= -8m² - 2mn + 15n²

5.(3b-2b²+4)(5-b)
=(3b)(5) + (-2b²)(5) + 4(5) + (3b)(-b) + (-2b²)(-b) + (4)(-b)
= 15b - 10b² + 20 - 3b² + 2b³ - 4b
= 2b³ - 10b² - 3b² + 15b - 4b + 20
= 2b³ - 13b² + 11b + 20

6.2a(2a-7b)-2(3a²-4ab+5)
= [2a(2a) + 2a(-7b)] - [2(3a²) + 2(-4ab) + 2(5)]
= (4a² - 14ab) - (6a² - 8ab + 10)
= 4a² - 14ab - 6a² + 8ab - 10
= 4a² - 6a² - 14ab + 8ab - 10
= -2a² - 6ab - 10

2007-01-31 19:46:34 補充：
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