Use the permutation formula to solve a problem when n = 8 and r = 2. A. 56
B. 672
C. 6,720
D. 40,320

Option A. 56

Step-by-step explanation:

From the question given above, the following data were obtained:

Total number (n) = 8

Item taken for permutation (r) = 2

Pemutation (P) =?

ₙPᵣ = n! / (n – r)!

₈P₂ = 8! / (8 – 2)!

₈P₂ = 8! / 6!

₈P₂ = 8 × 7 × 6! / 6!

₈P₂ = 8 × 7

₈P₂ = 56

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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)