Test missile #1 and test missile #2 are headed straight toward each other. Missile #1 is
traveling at 950 feet per second, and missile
#2 is traveling at 1,000 feet per second. If
the two missiles are 7,800 feet apart, how
many seconds will it be before they meet?

a. the residual plot for model 1 has a random pattern and is a good fit for the data.

answer: a.   one is a factor of every whole number since every number is divisible by itself.

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