Question

8- Considere a função real f(x) = 4x² + 3x – 7. Determine:

a) f(2) =

b) f(-1) =

c) o valor de x quando f(x) = 0 me ajudem por favor =(​

Answer 1

f(x) = 4x² + 3x – 7.

a) f(2) =4.2² +3.2 -7 = 16 +6 -7 = 22 -7 = 15

b) f(-1) =4.(-1)² +3.(-1) -7= 4 -3 +7 =1 +7= 8

c) 4x² + 3x – 7 = 0

∆=b²-4ac= 3² -4.4.(-7)= 9 +112= 121 => √∆=11

x = -b±√∆/2a

x = -3±11/2.4

x' = -3+11/8 = 8/8 = 1 ✓

x" = -3-11/8 = -14/8 :(2/2) = -7/4 ✓