Question

dada a função f (x)= -x²+9x-8, determine os valores reais de x para que se tenha:
f(x)=10;
f(x)=11;
f(x)=-15/4
​

Answer 1

Resposta:

Explicação passo a passo:

f(x)=10

-x²+9x-8=10

-x²+9x-18=0

a=-1

b=9

c=-18

x=-9+-V9²-4.-1.-18/2.-1

x=-9+-V81-72/-2

x=-9+-V9/-2

x=-9+-3/-2

x'=-9-3/-2=-12/-2=6

x''=-9+3/-2=-6/-2=3

f(x)=11

-x²+9x-8=11

-x²+9x-19=0

a=-1

b=+9

c=-19

x=-9+-V9²-4.-1.-19/2.-1

x=-9+-V81-76/-2

x=-9+-V5/-2

x'=-9+V5/-2

x''=-9-V5/-2

f(x)=-15/4

-x²+9x-8=-15/4

-x²+9x-32/4+15/4=0

-x²+9x-17/4=0

a=-1

b=9

c=-17/4

x=-9+-V9²-4.-1.-17/4/2.-1

x=-9+-V81-17/-2

x=-9+-V64/-2

x=-9+-8/-2

x'=-9-8=-2=-17/-2=17/2

x''=-9+8/-2=-1/-2=1/2

S={1/2;17/2}