This is what I did but I can't seem to get the answer $\displaystyle y = \frac{49}{12} - 3(x + \frac{5}{6})^2$Express $\displaystyle y = 2 - 5x - 3x^2$ in the form $\displaystyle y = a - b(x + c)^2. $Hence find the maximum value of y and the corresponding value of x.

$\displaystyle y = 2 - 5x - 3x^2$

$\displaystyle y = -3 (x^2 + \frac{5}{3}x - \frac{2}{3})$

$\displaystyle y = -3 [(x + \frac{5}{6})^2 - \frac{2}{3} + \frac{23}{56})]$

$\displaystyle y = -\frac{1}{12} - 3(x + \frac{5}{6})^2$

Is there a careless mistake somewhere that I can't seem to spot? I've been redoing this for at least four times and I can't seem to see where I've gone wrong ):

Any help would be greatly appreciated and thank you very much in advance.