The expression $x^2 + 3x - 28$ can be written as $(x + a)(x - b),$ and the expression $x^2 - 10x - 56$ written as $(x + 2b)(x + c)$, where $a$, $b$, and $c$ are integers such that $c > 0.$ What is the value of $2c - a$?
x^2 + 3x - 28 = ( x + (-4) ) ( x - ( - 7 ) ) a = -4 b = -7
x^2 - 10x - 56 = (x - 14 ) ( x + 4) = ( x + 2(-7) ) ( x + 4) c = 4
So
2c - a =
2(4) - (-4) =
8 + 4 =
12
+383 
