HEELLLPP

x^2+4x-5x^2-1

You have to look for commmon terms

4x^2+4x-1

And you have a cuadratic equation

x²+4x-5x²-1

= -4x² + 4x - 1

= $-4(x^{2}-x+\frac{1}{4})$

= $-4(x - \frac{1}{2})(x - \frac{1}{2})$

= $-4(x - \frac{1}{2})^{2}$