## Algebra and Trigonometry 10th Edition

One that opens upwards: $y=x^2-3x-4$ One that opens downwards: $y=-x^2+3x+4$
Use: $y=a(x-x_1)(x-x_2)$, where $x_1$ and $x_2$ are the $x$ of the x-intercepts. $y=a[x-(-1)](x-4)=a(x^2-4x+x-4)=a(x^2-3x-4)$ One that opens upwards ($a\gt0$). $y=1(x^2-3x-4)=x^2-3x-4$ One that opens downwards ($a\lt0$). $y=-1(x^2-3x-4)=-x^2+3x+4$