S1 Maths 快 20點!!!

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(9)[(-12)-(-5)]×6+(-8)

=[(-12+5)](6)+(-8)

=(-7)(6)+(-8)

=(-42)+(-8)

=(-42-8)

=(-50)

=-50


先抄第9題 稍後找上10,11

9計算[(-12)-(-5)]×6+(-8)。(列明計算步驟)

= -7 x 6 -8
= -42 - 8
= -50


10 用補償策略估算2049×81

= 2050 x 80
= 164000


11 解方程2分之z-1 +3=5 (列明計算步驟)

(z-1)/2 + 3 = 5
(z-1)/2 = 2
z-1 = 4
z = 5


12 展開 (-4x+5y)(y+x) (列明計算步驟)

= y(-4x+5y) + x(-4x+5y)
= -4xy + 5y^2 - 4x^2 + 5xy
= 5y^2 + xy - 4x^2


13 解方程 x+2=3分之1 (9x-2) (列明計算步驟)
x+2 = (9x-2)/3
3x+6 = 9x-2
6+2 = 9x - 3x
8 = 6x
8/6 = x
4/3 = x
x = 4/3


14 小明有一些$1及$5硬幣。已知$1硬幣的數目為$5硬幣的3倍。若硬幣的總值為$104，求$5硬幣數量 (列明計算步驟)

設A為$5硬幣數量
A x 5 + 3A x 1 = 104
5A + 3A = 104
8A = 104
A = 13


15小明以$288售出了80枝筆。若交易的盈利百分數為20%，求售出每枝筆的盈利(列明計算步驟)

成本 = 288/(1+20%)

盈利 = 288 - 288/(1+20%)

每枝筆的盈利 : [288 - 288/(1+20%)]/80
= (288 - 240) / 80
= 48/80
= 0.6

11.2分之z=5-3+1
2分之z=3
z=3x2
z=6
12. (-4x+5y)(y+x)
= (-4x+5y)y+ (-4x+5y)x
= (-4xy+5y2次方) + (-4x2次方+5xy)
= -4xy+5y2次方 - 4x2次方+5xy
= xy+5y2次方-4x2次方

13. x+2=3分之1 (9x-2)
x+2=3分之9x-2
3(x+2)=9x-2
3x+6=9x-2
6+2=9x-3x
8=6x
8分之6=x
x=8分之6
14. Let y be the member of $5
3y+5y=104
8y=104
y=13
15. 288*20%÷80
=0.72