F.3...百分法&因式分解(超易的)

(4a) x^2 - 18x + 65
= x^2 - 13x - 5x + 65
= x(x - 13) - 5(x - 13)
= (x - 13)(x - 5)
(4b) (a+1)^2 - 18(a + 1) + 65
= [(a+1)-13][(a+1)-5]
= (a - 12)(a - 4)
(5) 2x^2 - 13xy + 21y^2
= 2x^2 - 7xy - 6xy + 21y^2
= x(2x - 7y) - 3y(2x - 7y)
= (2x - 7y)(x - 3y)
(6) 遊戲機售價 = $1250 * (1 - 35%)
= $812.5
(7a) 下月薪金 = $18000 * (1 + 8%) * (1 - 4%)
= $18000 * 1.08 * 0.96
= $18662.4
(b) 月薪百分變化
= (18662.4 - 18000)/18000 * 100%
= 3.68% (增加)
(8) 半年利率 = 5%/2 = 0.025
三年後本利和
= $20,000 * (1 + 0.025)^6
= $23,193.87
複利息 = $23,193.87 - $20,000 = $3,193.87
(9a) 每千克菊普售價 = $30 * (3/8) + $45 * (5/8)
= $39.38
(b) 菊花新售價 = $30 * (1 + 12%) = $33.6
普洱新售價 = $45 * (1 - 5%) = $42.75
每千克菊普新售價 = $33.6 * (3/8) + $42.75 * (5/8)
= $40.58
(10) 應課稅入息實額 = $264000 - $108000 = $156000
首$35000稅額 = $35000 * 2% = $700
第二$35000稅額 = $35000 * 7% = $2450
第三$35000稅額 = $35000 * 12% = $4200
餘額 = $156000 - 3*35000 = $51,000
稅額 = $51,000 * 17% = $8670
總稅款 = 700 + 2450 + 4200 + 8670 = $16,020

2009-12-29 14:29:33 補充：
同意id55556的修正,謝謝

nelsonywm2000第9題b好似按錯計算機...9c就未做

b)一千克菊普新的售價=3[30(1+12%)/8]+5[45(1-5%)/8]
=12.6+26.71875
=($)39.31875

c)百分改變=(新值-舊值)/舊值 X 100%
=(39.31875-39.375)/39.375 X 100%
=-0.143% (準確至小數點後三個位)
所以一千克菊普的售價減少了百分之0.143