Given right triangle A
B
C
ABC with altitude
B
D
‾
BD
drawn to hypotenuse
A
C
AC. If
A
D
=
3
AD=3 and
A
C
=
13
,
AC=13, what is the length of
A
B
‾
AB
in simplest radical form? (Note: the figure is not drawn to scale.)

i would say c is the best answer, hope it's right!

good luck! =)

cutie~

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)