Answer:
f(-4)= -55
Step-by-step explanation:
We want to find f(x), or y, when x is equal to -4.
Therefore, we can substitute -4 in for x in the function.
f(x) = -2x^2 + 4x - 7
Substitute -4 in for x
f(-4) = -2(-4^2) + 4(-4) - 7
Evaluate the exponent
f(-4)=-2(16)+4(-4)-7
Multiply -2 and 16
f(-4)= -32+4(-4)-7
Multiply 4 and -4
f(-4)=-32-16-7
Subtract
f(-4)=-55
Answer:
The mean is also increased by the constant k.
Step-by-step explanation:
Suppose that we have the set of N elements
{x₁, x₂, x₃, ..., xₙ}
The mean of this set is:
M = (x₁ + x₂ + x₃ + ... + xₙ)/N
Now if we increase each element of our set by a constant K, then our new set is:
{ (x₁ + k), (x₂ + k), ..., (xₙ + k)}
The mean of this set is:
M' = ( (x₁ + k) + (x₂ + k) + ... + (xₙ + k))/N
M' = (x₁ + x₂ + ... + xₙ + N*k)/N
We can rewrite this as:
M' = (x₁ + x₂ + ... + xₙ)/N + (k*N)/N
and (x₁ + x₂ + ... + xₙ)/N was the original mean, then:
M' = M + (k*N)/N
M' = M + k
Then if we increase all the elements by a constant k, the mean is also increased by the same constant k.
Answer:
<em>24 children</em>
Step-by-step explanation:
If the length of time, y hours, it takes to put a jigsaw puzzle together is inversely proportional to the number of children, x, this is represented as;
k is the constant of proportionality
If it takes 16 children 6 hours to put the jigsaw puzzle together, this means at x = 16, y = 6
Substitute:
6 = k/16
k = 6*16
k = 96
W are to find number of children needed to put the same jigsaw puzzle together in 4 hours, this is done by substituting k = 96 and y = 4 into the expression y = k/x
y = 96/4
y = 24
<em>Hence it will take 24 children to put the same jigsaw puzzle together in 4 hours</em>
<em></em>
Let n = number of glasses needed
1 glass gives us 1*0.4 = 0.4 liters of water
2 glasses give us 2*0.4 = 0.8 liters
3 glasses give us 3*0.4 = 1.2 liters
4 glasses give us 4*0.4 = 1.6 liters
and so on...
In general,
n glasses give us n*0.4 = 0.4*n liters of water
So 0.4*n is going to be the same as 3.4 as we want to fill the 3.4 liter pitcher.
Set 0.4*n equal to 3.4 and solve for n
0.4*n = 3.4
0.4*n/0.4 = 3.4/0.4 <<--- divide both sides by 0.4
n = 8.5
If we want n to be a whole number, then round up to the nearest whole number. So we'll need 9 full glasses of water to fill the 3.4 liter pitcher. There is extra water in this case which isn't used.
So the answer is either 8.5 or 9 depending on if your teacher wants you to round to the nearest whole number.
