A students grade varies directly with the amount of time spent studying. A student studies 30 minutes and earns a grade of 50%. If he or she studies for 45 minutes, what grade is most likely to be earned?

explanation:

step-by-step explanation:

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answer:   x (x+6)^2, choice b

discussion:

factor x out of the equation:

x^3 + 12x^2 + 36x = x (x^2 + 12x + 36).

note that 6+6 = 12 and 6*6 = 36 so the above factors into:

x (x+6)^2

which is choice b

you,

mrb