How do I find a greatest value ? C=-5x^2-4x+1

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Answer 1 · 2018-05-01T13:05:08

#9/5#

#C = -5x^-2 - 4x + 1#

Differentiating #C#

#rArr - (5 xx 2)x^(2 - 1) - (4 xx 1)x^(1-1) + 0= 0#

# -10x^1 - 4x^0 = 0#

Note: #a^0 = 1#

#-10x = 4#

#(-10x)/10= -4/10#

#x = -4/10#

#x = -2/5#

Substituting the value of #x# into the main equation;

#C = -5(-2/5)^2 - 4(-2/5) + 1#

#C = -5(4/25) + 8/5 + 1#

#C = -4/5 + 8/5 + 1#

#C = (-4+ 8 + 5)/5#

#C = 9/5#

Hence, #9/5# is the greatest value of #C#