The battery life for Bruhier’s cell phone is longer when he has fewer apps running. When only one app is running, the battery will last for 16 hours. When four apps are running, the battery will only last for 4 hours. This situation represents
variation.

The constant of variation, k, is equal to
.

If eight apps are running, Bruhier’s battery will last for
hours.

1hr

Step-by-step explanation:

you have to wait a while to reward brainliest if only one person answers. if 2 people answer there should be a "mark brainliest" on their question.

i cant fully remember all of the ranks, here are the ones i remember.

hand, ambitous, ace, genius.

x^2 + 81

we can factor this using difference of square binomials.

rewrite the equation:

x^2 - (-81)

factor:

(a^2 - b^2) = (√a^2 + √b^2)(√a^2 - √b^2)

(x^2 - (-81) = (x + √-81)(x - √-81)

we can remove the - from under the radical by multiplying it by i.

(x^2 - (-81) = (x + i√81)(x - i√81)

(x^2 - (-81) = (x + 9i)(x - 9i)

we can check our answer by using foil:

x^2 - 9ix + 9ix - 81i^2

x^2 - 81^2

i^2 = -1

x^2 + 81