The man is going to exit the stairwell at the 4th floor, which is at a height of 42 feet above ground level. Let t be equal to the number of second it takes for him to get to the 4th floor. Set up and solve an equation to find the value of t. Round your answer to the nearest tenth of a second.

-2 is the right

hi! i think the answer is 1/2 : )

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