SOLUTION: I need help solving the quadratic function,For Each Funtion:(a) determine whether the graph opens down or up, (b) find the axis of symmetry, (c)find the vertex, (d)find the y-inter

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: I need help solving the quadratic function,For Each Funtion:(a) determine whether the graph opens down or up, (b) find the axis of symmetry, (c)find the vertex, (d)find the y-inter      Log On


   

Question 214893: I need help solving the quadratic function,For Each Funtion:(a) determine whether the graph opens down or up, (b) find the axis of symmetry, (c)find the vertex, (d)find the y-intercept,(e) find the zeros, and (f) graph the function
the equation is: -(x+4)(x-2)
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
y+=+-%28x%2B4%29%28x-2%29
y+=+-%28x%5E2+%2B+2x+-+8%29
y+=+-x%5E2+-+2x+%2B+8
If the coefficient of the squared term is
negative (-1 in this case), then
the parbola opens down.
The axis of symmetry is at x+=+-b%2F%282a%29
when the general form of the equation is
ax%5E2+%2B+2b+%2B+c+=+0, so
a+=+-1
b+=+-2
x+=+-%28-2%29%2F%282%2A%28-1%29%29
x+=+2%2F%28-2%29
The axis 0f symmetry is x+=+-1
and, when x+=+-1,
y+=+-%28x%2B4%29%28x-2%29
y+=+-%28-1%2B4%29%28-1-2%29
y+=+-%283%2A%28-3%29%29
y+=+9
The vertex is at (-1,9)
also
y+=+-%28x%2B4%29%28x-2%29
0+=+-%28-4+%2B+4%29%28-4-2%29
There is a zero at x+=+-4
0+=+-%282+%2B+4%29%282-2%29
There is a zero at x+=+2
+graph%28+600%2C+600%2C+-5%2C+5%2C+-3%2C+12%2C-x%5E2+-+2x+%2B+8%29+