Answer:55x+
−3
20
Step-by-step explanation:
It does not matter whether or not you have a d or a c to use for an unknown number, because you do not know what that number is. The letter does not abbreviate something, it's just a symbol to fill in the place of the missing number.<span />
Hey Kayla!
Let me help you out real quick.
x - 2y = 5
-3x + 2y = 7
We need to solve x - 2y =5 for x
x - 2y = 5
x = 5 + 2y
Now substitute 2y + 5 for x in -3x + 2y = 7
-3x + 2y = 7
-3(2y + 5) + 2y = 7
-6y - 15 + 2y = 7
-4y - 15 = 7
-4y = 7 + 15
-4y = 22
y = 22/-4
y = -11/2
Now we need to substitute -11/2 for y in x= 2y + 5
x = 2y + 5
x = 2(-11/2) + 5
x = -22/2 + 5
x = -6
Thus,
The answer is x = -6 and y = -11/2
The correct answer is option D
Good luck with your studies :)
You got it!
<span />
Answer:
a) Var[z] = 1600
D[z] = 40
b) Var[z] = 2304
D[z] = 48
c) Var[z] = 80
D[z] = 8.94
d) Var[z] = 80
D[z] = 8.94
e) Var[z] = 320
D[z] = 17.88
Step-by-step explanation:
In general
V([x+y] = V[x] + V[y] +2Cov[xy]
how in this problem Cov[XY] = 0, then
V[x+y] = V[x] + V[y]
Also we must use this properti of the variance
V[ax+b] =
V[x]
and remember that
standard desviation = ![\sqrt{Var[x]}](https://tex.z-dn.net/?f=%5Csqrt%7BVar%5Bx%5D%7D)
a) z = 35-10x
Var[z] =
Var[x] = 100*16 = 1600
D[z] =
= 40
b) z = 12x -5
Var[z] =
Var[x] = 144*16 = 2304
D[z] =
= 48
c) z = x + y
Var[z] = Var[x+y] = Var[x] + Var[y] = 16 + 64 = 80
D[z] =
= 8.94
d) z = x - y
Var[z] = Var[x-y] = Var[x] + Var[y] = 16 + 64 = 80
D[z] =
= 8.94
e) z = -2x + 2y
Var[z] = 4Var[x] + 4Var[y] = 4*16 + 4*64 = 320
D[z] =
= 17.88