Question

How do you find the vertex of `y= -2(x+3)(x-1)`?

Answer 1

`"vertex "=(-1,8)`

Explanation:

`"the vertex lies on the axis of symmetry which is "`
`"positioned at the midpoint of the zeros"`

`"to find the zeros set "y=0`

`rArr-2(x+3)(x-1)=0`

`"equate each factor to zero and solve for "x`

`x+3=0rArrx=-3`

`x-1=0rArrx=1`

`x_"vertex"=(-3+1)/2=-1`

`"substitute this value into the equation for y"`

`y_"vertex"=-2(2)(-2)=8`

`rArrcolor(magenta)"vertex "=(-1,8)`