SOLUTION: f(x)= -4x^2-8x+3 is this a minmum or a maximum what is the value

Question 556504: f(x)= -4x^2-8x+3
is this a minmum or a maximum
what is the value
Answer by prateekagrawal(56) (Show Source): You can put this solution on YOUR website!
f(x) = -4x^2 -8x +3
f(x) = -4(x^2 +2x) +3
f(x)= -4 (x^2 + 2x +1 -1) +3
f(x)= -4(x+1)^2 -4(-1) +3
f(x) = -4(x+1)^2 +4 +3
f(x) = -4(x+1)^2 +7
here (x+1)^2 is a whole square term... which will always be positive.
so, -4(x+1)^2 is always negative.
so, at x= -1 , f(x) =7 this is the maximum value of this...
second method:
f(x)= ax^2 +bx +c
if a>0 then minimum value
and if a<0 then maximum value.
and value is = f(-b/2a)
.
so, here a=-4 <0 so, maximum value....
.
and value is -(-8)/2(-4) = -1.
so,
f(-1) = -4(-1)^2 -8(-1)+3
f(-1) = -4+8+3
f(-1) = 7.
RELATED QUESTIONS
what is the maximum value for the function... (answered by josgarithmetic)

f(x)=-2x^2+8x-12 does the function have a minimum or maximum value? where does the... (answered by MathLover1)

What is the maximum or minimum value of f(x)=2x^2-8x-3 and how do you find... (answered by josgarithmetic,ikleyn,TeachMath)

F(x)=2x^2-4x-5 Does this function have a maximum or minimum value What is the... (answered by josgarithmetic)

Does the quadratic function f(x) = -(x + 5)2 � 3 have a maximum or minimum value? What... (answered by Fombitz)

f(x)=x2 + 2x - 9 determine whether the given quadratic function has a minmum or... (answered by josmiceli)

Determine whether there is a maximum or minimum value for the given function, and find... (answered by Fombitz)

Find the maximum or minimum value of the function. f(x) = 3x^2 − 37 State whether (answered by MathLover1)

the general form of a quadratic equation is y= ax +bx+c 1 .draw the graph with... (answered by rwm)