maths question

Kei

2009-02-05 1:52 am

1.(a)Find the LCM of 3x square -3x, 2x square+x
(b)Hence simplify 3over3x square-3x-1over2x square+x

2.change the subject to d
S=BoverD(d)+10d

3.Factorize(a) -b square-c square-2bc
(b) x square-y square-z square-2yz

4.(a)if the length of a side of a square is 4.7cm correct to the nearest0.1cm find the lower limit and the upper limit of the perimeter of the square.

(b)hence, find the area of the square.

5.(a)a bottle of milk weighed 2kg,correct to the nearest 10g. Find the relative error.

回答 (1)

myisland8132

2009-02-05 2:19 am

✔ 最佳答案

1(a)
LCM of 3x^2 -3x, 2x^2+x is x(x-1)(2x+1)
(b)
3/(3x ^2-3x)-1/(2x^2+x)
=1/(x ^2-x)-1/(2x^2+x)
=[(2x+1)-x(x-1)]/x(x-1)(2x+1)
=(-x^2+3x+1))/x(x-1)(2x+1)
2
S=B/(Dd+10d)
S(Dd+10d)=B
d(D+10)=B/S
d=B/[S(D+10)]
3(a)
-b ^2-c^2-2bc
=-(b^2+c^2+2bc)
=-(b+c)^2
(b)
代b=y and c=z
x^2-y^2-z^2-2yz
=x^2-(y+z)^2
=(x+y+z)(x-y-z)
4(a)
the length of a side of a square is 4.7cm correct to the nearest0.1cm
Actual length is bound by (4,65,4,74)
lower limit of the perimeter of the square
=4.65*4
=18.6 cm
The upper limit of the perimeter of the square
=18.96 cm
(b) The area of the square
lower limit of the area of the square
=4.65^2
=21.6 cm^2 (correct to the nearest0.1cm )
The upper limit of the perimeter of the square
=4.74^2
=22.5 cm^2 (correct to the nearest0.1cm )
5 (a)
relative error
=10g/2kg
=10g/2000g
=1/200
=0.005

2009-02-04 18:20:17 補充：
0.005=0.5%

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