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B. x = 7; AB = 9, AC = 12

Step-by-step explanation:

12/4 = (x + 2)/(x - 4) (similar triangles theorem)

3 = (x + 2)/(x - 4)

Cross multiply

3(x - 4) = (x + 2)

3x - 12 = x + 2

Collect like terms

3x - x = 12 + 2

2x = 14

x = 14/2

x = 7

✔️AB = x + 2 = 7 + 2

AB = 9

✔️AC = (x + 2) + (x - 4) = (7 + 2) + (7 - 4)

AC = 9 + 3

AC = 12

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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