+283 I think this one is easy, but I sorta forgot how to get equations from graphs and all the equations and jazz ):
A parabola with equation y=x^2+bx+c passes through the points (-1, -11) and (3, 17). What is c?
+9464 y = x2 + bx + c
The graph of the equation passes through the point (-1, -11) so we know....
-11 = (-1)2 + b(-1) + c
-11 = 1 - b + c
Add b to both sides.
-11 + b = 1 + c
Add 11 to both sides.
b = 12 + c
The graph of the equation passes through the point (3, 17) so we know....
17 = (3)2 + b(3) + c
17 = 9 + 3b + c
Subtract 9 from both sides.
8 = 3b + c
And we know b = 12 + c so we can substitute 12 + c in for b .
8 = 3(12 + c) + c
Distribute 3 to the terms in parenthesees.
8 = 36 + 3c + c
Subtract 36 from both sides.
8 - 36 = 3c + c
Combine like terms.
-28 = 4c
Divide both sides by 4 .
-7 = c
