Question

dada a função quadratica f (x) = 2x²+ x - 1,determine:
a) f(-1) =
b) f(1) =
c) f(2) =
d) f(0) =
e) os valores reais de x para f(x) = 2​

Answer 1

Explicação passo-a-passo:

f(x)= 2x²+x - 1

a) f(-1)= 2.(-1)² +(-1) -1

f(-1)= 2.1-1-1

f(-1)= 2 -1-1

f(-1)= 1-1

f(-1)=0

b) f(1)= 2.1² +1 -1

f(1)= 2+1-1

f(1)= 3-1

f(1)=2

c) f(2)= 2.2² +2-1

f(2)= 2.4+2-1

f(2)= 8+2-1

f(2)= 10-1

f(2)=9

d) f(0)= 2.0² + 0 -1

f(0)= 2.0+0-1

f(0)= 0+0-1

f(0)= -1

e) 2= 2x²+x -1

0= 2x² +x -1-2

2x²+x-3=0

∆= 1² -4.2.(-3)

∆= 1 + 24

∆=25

x= - 1±√25/2.2

x= -1 ±5/4

x1= -1+5/4

x1= 4/4

x1=1

x2= -1-5/4

x2= -6/4

x2= -3/2