The linear equation:
y = k x + b
We will use first two values and solve the system of equations:
11 = k * 7 + b / *(-1)
13 = k * 8 + b
---------------------
-11 = - k * 7 - b
13 = k * 8 + b
----------------------
2 = k
13 = 16 + b
b = 13 - 16 = -3
y = 2 x - 3 ( y varies directly with x )
Cos (B) = (a^2 + c^2 -b^2) / (2 * a * c)
cos (B) = (11^2 +17^2 -12^2) / (2 * 11 * 17)
cos (B) = (121 + 289 -144) / (374)
cos (B) = 266 / 374
cos (B) =
<span>
<span>
<span>
0.7112299465
Angle B = </span></span></span>44.665 degrees
(x-8)(x+5)
First thing you do is put the X's into the parentheticals because it is x^2 meaning there are 2 factors with x's. Then, you wonder what factors of -40 could add to get -3. In this case, they are -8 and 5. -8 times 5 is -40 and -8 +5 is -3. Then, you just add -8 and 5 beside the x's in the parentheticals.
The answer has 131;1 minutes