F.2 math

a ) 5x(x-3)(x+4) - 2x²(x-3)
=(5x²-15x)(x+4) - (2x³-6x²)
=(5x³+20x²-15x²-60x) - 2x³+6x²
=3x³+11x²-60x
=(x-3)(3x+20)

b ) (x+y)²-(x-y)²
=[x+y-(x-y)] [x+y+(x-y)]
=(2y) (2x)
=4xy

c ) n(n+2)(n+3)
=(n²+2n)(n+3)
=n³+3n²+2n²+6n
=n³+5n²+6n
=(n+3)(n+2)

d ) a³xa^5÷a^6
=a^(3+5)÷a^6
=a^(8-6)
=a²

e ) (a²)³(a^4)^5÷(a³)^4
=a^6 x a^20 ÷a^12
=a^(6+20-12)
=a^14

f) (a^-2)³ ÷ (a^-3)²
=( 1/a^2)³ ÷ (1/a³)²
=1/a^6 ÷ 1/a^6
=1

g) (ab)^6÷a²b^4÷a^4xb²
= a^6 b^6÷a²b^4÷a^4xb²
=a^(6-2) b^(6-4)÷a^4xb²
=a^4b² ÷ a^4 b²x
=1/x

h) (a²/b)³ x (b²/a)²
= a^6 b^3 x b^4/a²
=a^(6-2) b^(4+3)
=a^4 b^7

i) (1/ab^-1)^-1
=(b/a)^-1
=a/b

希望幫到你^^

a ) 5x(x-3)(x+4) - 2x²(x-3)
=(5x²-15x)(x+4) - (2x³-6x²)
=(5x³+20x²-15x²-60x) - 2x³+6x²
=3x³+11x²-60x
=(x-3)(3x+20)
b ) (x+y)²-(x-y)²
=[x+y-(x-y)] [x+y+(x-y)]
=(2y) (2x)
=4xy
c ) n(n+2)(n+3)
=(n²+2n)(n+3)
=n³+3n²+2n²+6n
=n³+5n²+6n
=(n+3)(n+2)

d ) a³xa^5÷a^6
a^(3+5)÷a^6
=a^(8-6)
=a²

e ) (a²)³(a^4)^5÷(a³)^4
=a^6 x a^20 ÷a^12
=a^(6+20-12)
=a^14

f) (a^-2)³ ÷ (a^-3)²
=( 1/a^2)³ ÷ (1/a³)²
=1/a^6 ÷ 1/a^6
=1

g) (ab)^6÷a²b^4÷a^4xb²
= a^6 b^6÷a²b^4÷a^4xb²
=a^(6-2) b^(6-4)÷a^4xb²
=a^4b² ÷ a^4 b²x
=1/x

h) (a²/b)³ x (b²/a)²
= a^6 b^3 x b^4/a²
=a^(6-2) b^(4+3)
=a^4 b^7

i) (1/ab^-1)^-1
=(b/a)^-1
=a/b

a)
5x(x-3)(x+4)-2x²(x-3)
=(x-3)(5x(x+4)-2x²)
=(x-3)(5x²+20x-2x²)
=(x-3)(3x²+20x)

b)
(x+y)²-(x-y)²
=(x²+2xy+y²)-(x²-2xy+y²)
=4xy

c)
(n+2)+(n+4)+(n+6)
=3n+12

d)
a³xa(5次)÷a(6次)
=a(3次+5次-6次)
=a²

e)
(a²)³x(a既4次)既5次÷(a³)既4次
=a(6次)xa(20次)÷a(12次)
=a(6次+20次-12次)
=a(14次)

f)
(a既-2次)³ ÷ (a既-3次)²
=(a既-6次) ÷ (a既-6次)
=1

g)
(ab)既6次÷a²b既4次÷a既4次xb²
=(a既6次xb既6次)÷(a²b既4次)÷(a既4次)xb²
=a(6次-2次-4次)xb(6次-4次+2次)
=a(0次)xb(4次)
=b(4次)
不過你條題目如果係 (ab)既6次÷a²b既4次÷a既4次b²，第三舊野無個"x"，將會是：
(ab)既6次÷a²b既4次÷a既4次b²
=(a既6次xb既6次)÷(a²b既4次)÷(a既4次b²)
=a(6次-2次-4次)xb(6次-4次-2次)
=a(0次)xb(0次)
=1

h)
(a²/b)³x(b²/a)²
=( a(6次)/b³ ) x ( b(4次)/a² )
=a(4次)b

i)
你條題目是
1.. ( 1/( a (b既-1次) ) )既-1次 or
2.. ( 1/( ab )既-1次) ) )既-1次 or
3.. ( (1/ab)既-1次 ) 既-1次

如果是1..
( 1/( a (b既-1次) ) )既-1次
=(b/a)既-1次
=a/b
如果是2..
( 1/( ab )既-1次) ) )既-1次
=(ab)既-1次
=1/ab
如果是3..
( (1/ab)既-1次 )既-1次
=(1/ab)既(-1次x-1次)
=(1/ab)

(a) 3x三次+11x二次-60x

b)4xy

c) (n+2)(n+4)(n+6)

d)a二次x

e)a十四次

f)a

g)1

h)a四次b

i)1/ab



勸導你一句啦~~~抄數無前途呀~~唔明就要問~~而唔係抄黎為左交功課~~若你唔識既又做唔到你咪返去先問ms/sir~~~佢話你唔做既話~~你就用我果句撻佢同佢講~~佢一定會原諒你~~~仲會好用心咁教你添呀肯定~~~

2007-08-04 02:43:49 補充：
sorry第3題唔記得幫你展開~~~c)~~(n2次+6n+8)(n+6) n3次+12n2次+44n+48

2007-08-04 02:45:40 補充：
d)既我以為你x~~~所以ans應是a2次