Pl help m if u do ill give u a dollar Abby bought 3 sweaters that each cost the same amount and 1 skirt that cost $15. The items she bought cost a total of $90 before tax was added. Determine which equation could be used to find, x, the cost of each sweater.
A 3x - 15 = 90
B 3x + 15 = 90
C 15 - 3x = 90
D 15x + 3 = 90

B

x is the price of the sweater so 3x  and add $15 for the skirt which would add up to $90

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)

the one below it is a function