Find the maximum or minimum of the following quadratic function: y = -2x2 + 4x - 1.
-1
0
1
4

Question

Find the maximum or minimum of the following quadratic function: y = -2x2 + 4x - 1.
-1
 0
 1
 4

anonymous · Answer

please help...

campbell_st · Answer

is this question algebra of calculus...?

campbell_st · Answer

ok... here is the the key, the parabola is concave down, since the coefficient of x^2 is -2


so for a quadratic $$ax^2 + bx + c = 0$$

the line of symmetry is 

$$x = \frac{-b}{2 \times a}$$

you have a = -2 and b = 4

the maximum of minimum lies on the line of symmetry

so find the value of x, and then substitute it into the original equation to find the max value

anonymous · Answer

I don't quite understand... I just need to know whether its a b c or d im learning how to do it I just don't have the time...

campbell_st · Answer

yes but to find it, a simple method is to find the line of symmetry and the substitute that value into the equation

campbell_st · Answer

and alternate method is to just graph the curve and read off the value.

anonymous · Answer

look im not like most people on here I know nearly nothing about math which is why im taking this class.. I don't have any idea what youre talking about and im stressing about this cause I need to pass...

campbell_st · Answer

ok... then use this site https://www.desmos.com/calculator type in the equation on the left and then read off the highest y value

anonymous · Answer

1?...

campbell_st · Answer

that correct.... 

the line of symmetry is x = -4/(2 x -2)   so x = 1

subsitute that value into the equation and you get 

y = -2 *(1)^2 + 4*(1) - 1

or 

y = 1

so the parabola is concave down, the you have a maximum at y = 1

anonymous · Answer

so one is the answer?

campbell_st · Answer

that's correct