SOLUTION: y= -x^2 + 9x - 2 which the first part is suppose to be a -x2 can someone help me with this.

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: y= -x^2 + 9x - 2 which the first part is suppose to be a -x2 can someone help me with this.      Log On


   

Question 733528: y= -x^2 + 9x - 2
which the first part is suppose to be a -x2
can someone help me with this.
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!
y=+-x%5E2+%2B+9x+-+2...here you have quadratic function or function of degree 2, graph is a parabola...in this case you have negative coefficient a in next to x%5E2 (you have -x%5E2 which means -1%2Ax%5E2); therefore, your parabola is "upside down" and has maximum
to solve it, set y=0 and use quadratic formula
0=+-x%5E2+%2B+9x+-+2
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+...note that a=-1, b=9, and c=-2

x+=+%28-9+%2B-+sqrt%289%5E2-4%2A%28-1%29%2A%28-2%29+%29%29%2F%282%2A%28-1%29%29+

x+=+%28-9+%2B-+sqrt%2881-%28-4%29%2A%28-2%29+%29%29%2F%28-2%29+

x+=+%28-9+%2B-+sqrt%2881-8+%29%29%2F%28-2%29+

x+=+%28-9+%2B-+sqrt%2873%29%29%2F%28-2%29+

x+=+%28-9+%2B-+8.54%29%2F%28-2%29+
solutions:

x+=+%28-9+%2B+8.54%29%2F%28-2%29+
x+=+%28-0.46%29%2F%28-2%29+
x+=+0.23+

x+=+%28-9+-8.54%29%2F%28-2%29+
x+=+%28-17.54%29%2F%28-2%29+
x+=+8.77+

+graph%28+500%2C+500%2C+-10%2C+10%2C+-10%2C+25%2C+-x%5E2+%2B+9x+-+2%29+