Question

A soma das raízes da equação -3x² + 30x – 72 = 0 é:


(A) 5
(B) 7
(C) 9
(D) 10
(E) -11

Answer 1

- 3X + 30X - 72 = 0

a= - 3....b= 30....c=-72

FORMULA DELTA

D = b^2 - 4 a c

D = (30)^2 - 4 (-3)(-72)

D = 900 + 12 (-72)

D = 900 - 864

D = 36

FORMULA DE BRASKARA

X = - b +,- \/D
......________
.............2a

X = - (30) +,- \/36
......___________
...............2(-3)

X = - 30 +,- 6
......________
............. - 6

X' = - 30 + 6
......._______
.............. - 6

X' = - 24
.......____
..........- 6

X' = 4

X" = - 30 - 6
........_______
..............- 6

X" = - 36
......._____
...........- 6

X" = 6

A SOMA DA DOIS RAIZES

Xtotal = X' + X"
X total = 4 + 6
X total = 10

A reaposta e a letra D)10