C
substitute a = - 1 into the expression
- (- 1) - 12(- 1)² = 1 - (12 × 1 ) = 1 - 12 = - 11 → C
Answer:
D. 
Step-by-step explanation:

To rewrite a mixed number as an improper fraction, first, multiply the whole number by the denominator.

Then, add this number to the numerator.

This number is now the numerator of the fraction. The denominator stays the same.

I hope this helps!
The variable b represents the area of the base of the prism or pyramid. Hope that helps!
Hey there! :)
Answer:
y = 11.
Step-by-step explanation:
Set both of the equations equal:
5x - 9 = x² - 3x + 7
Rearrange the equation:
0 = x² - 3x - 5x + 9 + 7
Combine like terms:
0 = x² - 8x + 16
Factor:
0 = (x -4)²
Solve for x:
0 = x - 4
x = 4.
Plug this into an equation to solve for 'y':
y = 5(4) - 9
y = 20 - 9
y = 11.
It should be an obtuse triangle
(hope this helps)