Solve the following system of equations by using substitution method
y= -3x-18
5x-2= -8
2007-12-15 12:39:49 · 21 answers · asked by CBrizz8807 1 in Science & Mathematics ➔ Mathematics
5x = -6 and 5 = -1.2
so
y=-3(-1.2) -18 y= 3.6-18
y= - 14.4
2007-12-15 12:41:55 · answer #1 · answered by Zach S 4 · 0⤊ 1⤋
Now, now, no frowny face after math question, math is fun!
y = -3x - 18
5x - 2 = -8
First, you solve for x
5x - 2 = -8
5x = -6
x = -6/5
And substitute in the first equation
y = -3(-6/5) - 18
y = 18/5 - 18
y = -72/5
2007-12-15 20:43:28 · answer #2 · answered by A A 3 · 1⤊ 0⤋
y= -3x-18
5x-2= -8
From the second equation we can get the value of x
5x-2= -8
5x = -8 + 2
5x = -6
x = -6 / 5
Now put this new value of x in first equation
y = -3x-18
y = -3(-6/5) -18
y = +18/5 - 18
y = +18/5 - 90/5
y = -72/5
therefor
x = - 6 / 5 = -1.2
y = - 72 / 5 = -14.4
2007-12-18 08:47:29 · answer #3 · answered by Rayan Ghazi Ahmed 4 · 0⤊ 0⤋
Make x the subject of the second formula
5x = -8+2 = -6
x = -6/5
Substitute into 1st formula:
y = -3*(-6/5) - 18
= 18/5 - 18
= - 14.4
2007-12-15 20:43:36 · answer #4 · answered by ozperp 4 · 0⤊ 0⤋
Given: y=-3x-18
5x-2=-8
Solution:
5x-2=-8
5x=-6
x=-6/5
y=-3(-6/5)-18
y=18/5 - 18
y= 3.6-18
y=14.4
(note: solved with calculator)
2007-12-15 21:21:04 · answer #5 · answered by eubert r 1 · 0⤊ 0⤋
ok, so in the first equation, you need to isolate the x.
So- y+18=-3x
y/3+6=x
now put this into the equation under that. so
5(y/3 +6)-2=8
5y/3+30-2=8
simplify and solve for y
5y/3+28=8
5y/3= -20
5y= -60
y = -12
now plug -12 in for Y in the 1st equation.
-12=-3x-18
6=3x
x=2
answer (2,-12)
2007-12-15 20:47:11 · answer #6 · answered by Ray 4 · 0⤊ 0⤋
take the second equation first because it has only one variable (just to make it that much easier to solve)....
5x-2=-8
solve for x.
5x-2=-8
+2 +2
5x=-6
Divide each side by 5 to get x by itself. x= -6/5
Now you have half of it done...
Plug x= -6/5 into the first equation, and solve for y.
y=-3x-18
y= -3 (-6/5) -18
y= -14.4
(-6/5 , -14.4)
Then you can use that and write it out whatever way your teacher wants
2007-12-15 20:46:21 · answer #7 · answered by kristen89129 2 · 0⤊ 0⤋
substitute the value of "y" into the second system:
5(-3x-18)-2= -8
-15x-90-2= -8
-15x-92= -8
-15x= 84
x=-5.6
substitute the value of "x" that you got from the second system into the first equation to get the value of "y" :
y= -3(-5.6)-18
y=16.8-18
y=-1.2
hope this helps! =]
2007-12-15 20:47:16 · answer #8 · answered by nelss 3 · 0⤊ 0⤋
y = -3x -18
+18 +18
18= -3x
18/-3 = -3/-3 x
-6 =x
y = -3x-18
y= -3(-6)x -18
y= -18 - 18
y=0
5x - 2 =-8
+2 +2
5x = -6
5/5 x = -6/5
x= -1.2
check
5x - 2= -8
5(-1.2) - 2 = -8
-6 - 2= -8
2007-12-15 20:54:56 · answer #9 · answered by Miss thing 2 · 0⤊ 0⤋
you find x from your second equation like this
5x=-8+2, 5x=-6,x=-6/5.
now you sub x into your first equation like this y=-3(-6/5)-18=18/5-18=-14.4
there you go !
2007-12-15 20:46:09 · answer #10 · answered by pralisa 3 · 0⤊ 0⤋
5x-2=-8
Solve this equation first.
add 2 to both sides
5x-2+2=-8+2
5x=-6
divide both sides by 5
5x/5=-6/5
x=-6/5=-1.2
Substitute this value in the other equation
y=-3(-1.2) -18
y= 3.6-18
y=-14.4
2007-12-15 20:46:26 · answer #11 · answered by Bec 2 · 0⤊ 0⤋