Sella is making a scale model of a monument that is 215 feet tall. she uses a scale of 1 inch = 5 feet. how tall should sella make her model?
21.5 inches
43 inches
215 inches
1075 inches

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

a is the best answer choice

2b2t

explanation:

2b2t

2b2t

explanation:

2b2t