michael0195 3 years ago Identify the domain and range for the graph of y = −2x2 − 8x + 1

1. myininaya

domain for all polynomials is all real numbers! :) now the best thing to do is put this into this form $y=a(x-h)^2+k$ to find the range This form is called vertex form by the way!

2. myininaya

or i guess you could look at visually but i don't care for that

3. myininaya

$y=-2(x^2+4x)+1$ $y=-2(x^2+4x+(\frac{4}{2})^2)+1+2(\frac{4}{2})^2$ Notice I added in a[b/2]^2 So I had to take it out! :) Now we have $y=-2(x+2)^2+1+2(\frac{16}{4})=-2(x+2)^2+1+8$ $y=-2(x+2)^2+9$ I see that the vertex is (-2,9) |dw:1331078112680:dw| That means the range is $[-\infty,9]$ Luis feedback group

4. michael0195

oh cool tyvm