Answer:
imaginary
Step-by-step explanation:

from the working strp, we know that the number is imaginary
we can't square root the negative number
Triangle area is 1/2 bh
So 11.9 is about 12, 7.1 is about 7.
7x12 = about 84 sq, cm
14. 36x^2 - 16
4(9x^2 - 4) =
4(3x + 2)(3x - 2) <==
15. 3x^2 + 10x - 8
(3x - 2)(x + 4) <==
16. 5x^2 - 16x + 15 = 4x - 5
5x^2 - 16x - 4x + 15 + 5 = 0
5x^2 - 20x + 20 = 0
5(x^2 - 4x + 4)
5(x - 2)(x - 2)
x - 2 = 0....x = 2