The Question:
y= -1.5x + 5000
y= x+1000
Solve simultaneously
My working:
-1.5x + 5000 = x + 1000
-2x = - 4000
x = 2000
If i substitute that back into the second equation y is 3000. but if I substitute it back into the first equation y is 2000 so obviously I stuffed up somewhere in my working but I can't figure out where. The answer is (1600, 2600) so can anyone tell me where I went wrong?
Simple Simultaneous Equations Question?
2008-07-15 8:56 am
回答 (10)
2008-07-15 9:00 am
✔ 最佳答案
x + 1000 = - 1.5 x + 50002.5 x = 4000
x = 4000 / 2.5
x = 1600
y = 1600 + 1000
y = 2600
x = 1600 , y = 2600
2016-05-25 12:25 am
A) 4x + y = 5 B) 3x - 2y = 12 multiply A by 2 so you get +2y which can be added to the -2y to eliminate it A) 8x + 2y = 10 + B) 3x - 2y = 12 = 11x = 22 divide by 11 so you get x = 2 sub x = 2 into one of the equation to find y so... 3x - 2y = 12 is also 6 - 2y = 12 and - 2y = 6 and hence y = -3 et voila (i think thats how you spell it)
2008-07-15 9:16 am
I am not screaming I am writing in caps so you can see what is mine and what is yours.
My working:
-1.5x + 5000 = x + 1000
-2x = - 4000
This is the step with the problem. You are either adding 1.5 xto both sides or subtracting x from both sides. That should be either 2.5 x on the right or -2.5x on the left.
x = 2000
My working:
-1.5x + 5000 = x + 1000
-2x = - 4000
This is the step with the problem. You are either adding 1.5 xto both sides or subtracting x from both sides. That should be either 2.5 x on the right or -2.5x on the left.
x = 2000
2008-07-15 9:14 am
y = -1.5x + 5000
y = x + 1000
y = -1.5x + 5000
x + 1000 = -1.5x + 5000
x + 1.5x = -1000 + 5000
2.5x = 4000
x = 4000/2.5
x = 1600
y = x + 1000
y = 1600 + 1000
y = 2600
∴ x = 1600 , y = 2600
y = x + 1000
y = -1.5x + 5000
x + 1000 = -1.5x + 5000
x + 1.5x = -1000 + 5000
2.5x = 4000
x = 4000/2.5
x = 1600
y = x + 1000
y = 1600 + 1000
y = 2600
∴ x = 1600 , y = 2600
2008-07-15 9:04 am
Look at what you ahve to do to the x on the right side of the equation
-1.5x+5000=1x+1000
-1x -1x
-2.5x=-4000
x =1600
-1.5x+5000=1x+1000
-1x -1x
-2.5x=-4000
x =1600
2008-07-15 9:03 am
/x=1600,y=2600
2008-07-15 9:01 am
Your process is correct but you made a mistake in addition. Note it carefully you will get the solution.
2.5x = 4000 x = 1600. This is the solution
2.5x = 4000 x = 1600. This is the solution
2008-07-15 9:00 am
You have -1.5x + 5000 = x + 1000, right? And then you ended up with -2x = -4000, which is wrong. When you transpose the x to the left side of the equation, you get:
-1.5x - x = 1000 - 5000
-2.5x = -4000
x = 1600
-1.5x - x = 1000 - 5000
-2.5x = -4000
x = 1600
2008-07-15 9:00 am
-1.5x minus x is not -2x. its -2.5x.
2008-07-15 9:00 am
-1.5x - 1x gives u -2.5x, not -2x... So i guess that's where you went wrong
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