Question

Se f(x) = x² - 9x + 8. calcule o valor de x de modo que se tenha f(x) = 0.

Answer 1

f(x)=x²-9x+8, f(x)=0
 x²-9x+8=0
-b±√b²-4ac/2a=
-(-9)±√(-9)²-4.1.8/2.1=
9±√81-32/2=
9±√49/2=
x'=9+7/2=8
x"=9-7=1

substituindo:
f(8)=x²-9x+8
f(8)=8²-9.8+8
f(8)=64-72+8
f(8)=-8+8
f(8)=0

f(1)=x²-9x+8
f(1)=1²-9.1+8
f(1)=1-9+8
f(1)=0