The mean of the numbers 3, 6, 4, x and 7 is 5. Find the standard deviation.

1.2

Step-by-step explanation:

Since (3 + 6 + 4 + x + 7)/5 = 5, then 3 + 6 + 4 + x + 7 equals 25. Adding, we have 20 + x = 25. Thus x = 5. Now we calculate how far each number is from the mean. 3 is 2 away. 6 is 1 away. 4 is also 1 away. 5 is 0 away, and 7 is 2 away. Now, we have to find the mean of this. (2 + 1 + 1 + 0 + 2 ) / 5 is equal to 6/5, which is 1.2

hello from mrbilldoesmath!

answer:   (7x + 6y) ( 49x^2 - 42xy + 36y^2)

discussion:

in general, the factorization of a^3 + b^3 is

a^3 + b^ 3 = (a + b) ( a^2 - ab + b^2)

in our case note that 343 = 7^3 and 216 = 6^3 so the equation becomes:

343x^3 + 216y^3 = (7x)^3 + (6y)^3

if you think of a (above) as 7x and b as 6y the factorization becomes

343x^3 + 216y^3 =

((7x + 6y) (   (7x)^2 - 7x*6y + (6y)^2)   =

(7x + 6y) ( 49x^2 - 42xy + 36y^2)

you,

mrb

(a + b) (a^2 - a b + b^2)

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