If -2d+5= -31, what is the value of 3d-9?
I need to know how you would do this...'cause I really have no idea what it's asking. Damn math! ( e_e)9
2007-12-14 22:40:17 · 7 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
-2d + 5 = -31 take 5 to the other side
-2d = -31 -5
-2d = - 36
d = -36/-2
d = 18
now substitute d = 18 in the other equation
3d - 9 =
3(18) - 9
= 54 - 9 =
45
simple
~~~
2007-12-14 22:45:36 · answer #1 · answered by A Little Sarcasm Helps 5 · 0⤊ 0⤋
Solve for d in the first equation
-2d + 5 = -31
=> -2d = -31 -5
=> -2d = -36
or d= 18
so substitute into 3d -9 gives
3d - 9= 3*18 - 9 = 54 -9 = 45
so 3d -9 = 45
2007-12-14 22:47:12 · answer #2 · answered by rsraszka 3 · 0⤊ 0⤋
If -2d+5= -31, what is the value of 3d-9?
it's asking you to use the first equation to find the value of "3d-9" so first you have to use the first equation to find the value of "d".
finding "d":
-2d+5=-31
first you move "-2d" over to the other side so that it is positive. you do this by add 2d to both sides.
-2d+2d+5=-31+2d
so you get 5=-31+2d
then you move the -31 over to the other side.
5+31=-31+31+2d
which gives you
36=2d
then you divide both sides by 2
36/2=2d/2
giving you 18=d
now that you have d, just put it in!
d=18
3d-9
replace "d" with 18
3x18-9=54-9
and 54-9 is 45,
so the value of 3d-9 is 45!
hope that helped! :D
2007-12-14 22:53:41 · answer #3 · answered by Anonymous · 0⤊ 0⤋
1.
-2d+5 = -31
-2d = -31-5
-2d = -36
d = -36/-2
d = 18
2.
3d-9 = 3x18-9
3d-9 = 54-9
3d-9 = 45
2007-12-15 01:46:04 · answer #4 · answered by An ESL Learner 7 · 0⤊ 0⤋
-2d + 5 = -31
(move 5)
-2d = -36
(multiply both sides by 3/2)
-3d = -54
(multiply both sides by -1)
3d = 54
(subtract 9 from both sides)
3d-9 = 54-9
(solve)
3d-9 = 45
2007-12-14 22:45:32 · answer #5 · answered by wah b 2 · 0⤊ 1⤋
45
2007-12-14 22:47:48 · answer #6 · answered by omnisource 6 · 0⤊ 0⤋
first dind d in -2d+5-=-31
then d=18
substitute it to 3d-9
the answer is 45
2007-12-14 22:53:46 · answer #7 · answered by Anonymous · 0⤊ 0⤋