In which proportion does x have a value of 4?

B

Step-by-step explanation:

Using the method of cross- multiplication

A

7x = 252 ( divide both sides by 7 )

x = 36 ≠ 4

B

21x = 84 ( divide both sides by 21 )

x = 4

C

5x = 2 ( divide both sides by 5 )

x = 0.4 ≠ 4

D

5x = 200 ( divide both sides by 5 )

x = 80 ≠ 4

The proportion where x = 4 is B

they can both be solutions depends on the equation

step-by-step explanation:

what is the equation? ?

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)