Question

求！！高人！！解决英文的数学题！！！！拜托啊！！！！！！！1 好的我追加分数！！！

1. Ben has four more than twice as many CDs as Jack . If they have a total of 31 CDs , how many CDs does Jack have ?
2. Jack wants to replace the flooring in his rectangular Kitchen . He calculates the area of the floor to be 12.8 square meters , The actual area of the floor is 13.5 square meters . What is the relative error in calculating the area of the floor , to the nearest thousandth?
3.A right triangle contains a 38° angle whose adjacent side measures 10 centimeters. What is the length of the hypotenuse , to the nearest hundredth of a centimeter ?
4.On the set of axes below , graph and label the equations y=|x| and y=3|x| for the interval -3小等于x小等于3.（要图啊！）
5.On the set of axes below , solve the following system of equations graphically and state the coordinates of all points in the solution set . y=-x²+6x-3 x+y=7.(要图）

Answer 1

都很简单的题目
1. Ben has four more than twice as many CDs as Jack . If they have a total of 31 CDs , how many CDs does Jack have ?
Ben 的CD是Jack的2倍还多4张，如果他们一共有31张CD，那问Jack有几张CD？
x+2x+4=31 ===> x = 9

2. Jack wants to replace the flooring in his rectangular Kitchen . He calculates the area of the floor to be 12.8 square meters , The actual area of the floor is 13.5 square meters . What is the relative error in calculating the area of the floor , to the nearest thousandth?
Jack想重新装修一下他家厨房的地板，他算了一下他家的地板面积是12.8平米，可实际上正确答案是13.5平米。Jack测量的相对误差是多少，答案精确到千分之一。
(13.5-12.8)/13.5 = 0.051851851851851816 = 0.052

3.A right triangle contains a 38° angle whose adjacent side measures 10 centimeters. What is the length of the hypotenuse , to the nearest hundredth of a centimeter ?
一个直角三角形有一个角是38度，对边是10cm，问斜边的长度。
sin (38*3.14/180) = 对边 / 斜边
====> 斜边 = 16.2427 cm
这个题如果是不准带计算器的话，有点难度，要用三角函数的近似
sin[38] = sin[30+8] = sin[30]cos[8] + sin[8]cos[30]
sin[30] = 1/2
cos[30] = sqrt(3)/2
角度比较小的时候
sin[x] = x-x^3/6, cos[x] = 1-x^2/2, x=角度*3.1416/180=0.14
带入到前面的式子中
sin[38] = ((1 - x^2/2)/2 + 1.732/2*(x - x^3/6))
10/sin[38] = 16.235 cm

4 画图 我用Mathematica 一句话搞定
Plot[{Abs[x], Abs[3 x]}, {x, -3, 3}, PlotStyle -> Thick]

5 画图 还是Mathematica 一句话搞定
Plot[{x^2 + 6 x - 3, 7 - x}, {x, -12, 4}, PlotStyle -> Thick]

追问

你能把Mathematica这个软件发给我吗？我到处去下都没有下到。我的邮箱是 767215018@qq.com。谢谢啦！！！

Answer 2

本有比杰克2倍多四张的CD，如果他们一共有31张CD，问：杰克有多少张CD?
答：设杰克有X张CD，则本有(2X+4)张CD。
则有：X+2X+4=31 解得x=9
那么杰克有CD:2*9+4=22（张）

Answer 3

同意以下观点