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Old 07-27-2007   #1
Prof. Fessor
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Default Math Question???!!? HELP!?

Could someone please explain clearly on how to solve this math problem.Instruction...Find the equation of a line that both passes through the point (-4,5) and is parallel to the line of the give equation.(1) y= - 3x + 1Thanks!The (1) is just a number 1(not part of equation)
 
Old 07-27-2007   #2
kota2509
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this is purely substitution method until you find a whole number.( 1y = -3x + 1 ) or ( y - 1 ) = -3x.so substitute y with 4 so ( 4 - 1 ) = -3xso x = 3/-3 = -1so the new co-ordinates that pass through ( - 4, 5 )is ( -1, 4 ) where x = -1 and y = 4
 
Old 07-27-2007   #3
liebesmord
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If it is parallel, it will have the same slope. you can find the slope of your first equation by thinking of the equation y=mx+b, where m is your slope (So your slope would be -3). The easiest way to solve this is to draw a graph and plot your first line, then plot your second line. Once you figure out where your y-intercept is (where your line crosses the y, or vertical, axis), you can write your equation using y=mx+b (x and y are your coordinates, so you'd leave those as x and y, m is your slope which is -3, and b is your Y-intercept).
 
Old 07-27-2007   #4
KECHEN
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Ok first of all, if the equations are parallel, you know the slopes are the same and the slope for the first equation is -3.Now you just need to find the y-intercept for the point (-4,5) which is (0,-7) i think. Now you have everything you need so your equation should be y= -3x-7
 
Old 07-27-2007   #5
danish
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The answer is y= -3x -7, meaning negative three times "x" then subtract that by 7. You can find this out by typing the given equation into the calculator and see the line, then find the slope of that equation which is negative three, and then find another point on the other line other than (-4, 5) so the slope is -3, then plot that into the calculator along with (-4,5) and then use linreg to find the equation. That's it
 
Old 07-27-2007   #6
historian
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Let's put all this together and figure it out rather than punching buttons on a calculator.The slopes are the same if the two lines are parallel, as the other answers said.y=mx+b, where x and y are value of each point on the line, m is the slope and b is the y-intercept, the place where the line crosses the y axis.So in the original equation, the slope is -3. To be parallel, the slope of the new line must also be -3, so for the equation of the new line, we already know that y= -3x+b.We also know the x and y values of a point on the new line, so let's solve for b.5 (the y value) = (-3)(-4) [slope times x value] +b.5=12+b, so b= -7.Now we have the equation of the second line: y+-3x-7.
 
 

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