The test scores of the students in Mr. Duffy's class are shown on the line plot below. Most of the students in Ms. Guzman's class scored higher than most of the students in Mr. Duffy's class on the same test. Which line plot could represent the test scores of the students in Ms. Guzman's class?

hello from mrbilldoesmath!

answer:

(7 x + 6 y) (49 x^2 - 42 x y + 36 y^2)

discussion:

the trick is to recognize that 343 = 7^3 and 216 = 6^3 and, in general,

a^3 + b^3 =   (a + b) (a^2 - a b + b^2).

in our case

343x^3+216y^3   =   (7x)^3 + (6y)^3

so take a = 7x and b = 6y in the above equation to get the answer.

you,

mrb