Aparabola with equation y=x^2+bx+c passes through the points (-1,-11) and (3,17). what is c?

We can set up a system of equations in terms of b and c, using the given form of  .======for (-1,-11), this means that when x is -1, y should be -11.      so  is our first equation.for  (3,17)  this means that when x is 3, y should be 17.      so  is our second equation.we have the following system:       we can solve this by addition. if we multiply both sides of equation (i) by 3 we get      adding this with equation (ii) gets us      so c = -7.of course, you could use this to solve for b, and then use both b and c to create the equation to confirm that the conditions are met. but the question only cares about c.