how do i tackle the above?
what is the step by step guide?
2007-08-23 10:29:30 · 8 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
Equate both the expressions to find the value of x,
x + 7 = -2x - 2
3x = -9
x = -3
y = -3 + 7
y = 4
(-3, 4) is the point.
2007-08-23 10:35:16 · answer #1 · answered by Anonymous · 2⤊ 1⤋
You can either plot both on a graph, and see where the lines meet (which would show where the value of each equation is the same), or you can just solve them. They are both for Y in relation to X, so you need to find a value of X for which X+7=-2X-2.
If you want to plot them manually, use a set of X values, and work out the Y values from each equation, then plot the points defined by this and join them up. They are both straight lines, so this is very straightforward.
2007-08-23 17:39:43 · answer #2 · answered by misfratz 2 · 0⤊ 0⤋
In this case it would be easiest to eliminate 'y' by subtraction.
So!!!
AS y = x + 7 it also equals -2x - 2
Therefore
+y = x + 7
-y = 2x + 2 (NB change of signs)
_________
0 = 3x + 9
3x = -9 (Divide through by '3')
x = -3
To find 'y' take either equation
and substitute -3 for x
So!!!
y = -2(-3) - 2 (ritten like this means -2 x -3.)
y = +6 - 2 NB . '--' gives a '+' answer.
y = 4
So the two lines intersect at (-3, 4)
2007-08-24 15:25:27 · answer #3 · answered by lenpol7 7 · 0⤊ 0⤋
y = x + 7 and y = -2x - 2
Where the two lines intersect, the x and y values must be the same.
x + 7 = -2x - 2
x + 2x = -2 - 7
3x = -9
x = -3
Sub x=-3 into y = x + 7,
y = -3 + 7
y = 4
The two lines intersect at (-3, 4).
2007-08-24 20:47:05 · answer #4 · answered by Kemmy 6 · 0⤊ 0⤋
y = x + 7 and y = -2x - 2
Simultaneous equations
x - y + 7 = 0
-2x -y - 2 = 0
(i) Multiply topline by 2 and add the second line and calculate y
2x - 2y + 14 = 0
-2x -y - 2 = 0
-3y +12 = 0
-3y = -12
y = 4
(ii) Calculate x
x - 4 + 7 = 0
x+3 = 0
x=-3
(-3,4) is where they intersect.
2007-08-24 06:09:12 · answer #5 · answered by Joe H 2 · 0⤊ 0⤋
First, set the expressions equal to eachother, you have 2 expressions for y.
x + 7 = -2x - 2
Then, collect terms... move x terms to the left and numbers to the right. Solve for x.
3x = -9
x = -3.
Then, plug that expression for x into either equation to get the corresponding value for y. You'll get the same answer in both.
y = -3 + 7
y = 4.
So, your point of intersection is (-3,4)
2007-08-23 17:36:57 · answer #6 · answered by kvolcom13 3 · 0⤊ 0⤋
y = x + 7 and y = -2x - 2
x + 7 = -2x - 2
x + 2x = -7 -2
3x = -9
x = -3
So they intersect in x=-3 and y = f(-3) = 4
2007-08-23 17:36:18 · answer #7 · answered by lindsay 1 · 0⤊ 0⤋
x + 7 = - 2x - 2
3x = - 9
x = - 3
y = 4
Intersect at (- 3 , 4)
2007-08-27 11:34:40 · answer #8 · answered by Como 7 · 0⤊ 0⤋