Simultaneous Linear Equa

蔡小琳

2012-02-19 6:39 am

1. Michelle has some $5-coins and $2-coins. Given that the number of $5-coins is greater than that of $2-coins by 10, and the total value of the coins is $365, how many $5-coins she has?

2. x+y=3
x-2y=-2

3. Given that the equation x+2y=c passes through point (2,1). Points A and B are the intersecting points at which the graph cuts the x-axis and y-axis respectively.
Q: Find the coordinates of A and B.

回答 (1)

[匿名]

2012-02-20 10:46 am

✔ 最佳答案

1. 5x + 2y = 365
x - y = 10 (change it to 2x - 2y = 20)
add them together, 7x = 385, x = 55. Michelle has 55 $5 coins

2. x + y = 3 (multiply by 2: 2x + 2y = 6)
x - 2y = -2
add them together: 3x = 4
x= 4/3, plug x back to first equation: 4/3 + y = 3, y = 5/3

3. not sure what it means when it says "cuts the x-axis and y-axis," do you mean passing through? @_@

x + 2y = c (2,1), plug in (2,1): 2 + 2(1) = c, c = 4
x + 2y = 4
to find A and B you set x = 0 and y = 0 (points that pass through the x and y axis)
when x= 0, 2y=4, y = 2
when y = 0, x = 4
point A (pass through x axis) = (4,0)
pass B (pass through y axis) = (0,2)

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