Question

Tentukan akar-akar persamaan kuadrat berikut dengan cara menggunakan rumus ABC
a).X ² + 9x + 20 = 0
b).2x ² - X - 3 = 0
c).-3x ² + 2x + 5 = 0
Tlg dijawab y.soal'y bsok dikumpul.jgn lupa tulis cara kerja'y jg y..makasih

Answer 1

Rumus ABC
X1,2 = - b +/- akar (b^2 - 4ac) / 2a


1) x^2 + 9x + 20 = 0
X1,2 = - 9 +/- akar (9^2 - 4.1.20) / 2.1

X1,2 = - 9 +/- akar (81 - 80) / 2

X1,2 = - 9 +/- akar (1) / 2

X1,2 = - 9 +/- 1 / 2

X1 = (-9 - 1) / 2 = - 10/2 = - 5 atau

X2 = (-9 + 1)/2 = -8/2 = - 4


2) 2x^2 - x - 3 = 0

X1,2 = -(-1) +/- akar ((-1)^2 - 4.(2).(-3)) / 2.(2)

X1,2 = 1 +/- akar (1 + 24) / 4

X1,2 = 1 +/- akar (25) / 4

X1,2 = 1 +/- 5 / 4

X1 = (1 - 5) / 4 = - 1 atau

X2 = (1 + 5) / 4 = 3/2


3) -3x^2 + 2x + 5 = 0

X1,2 = -(2) +/- akar ((2)^2 - 4.(-3).(5)) / 2.(-3)

X1,2 = -(2) +/- akar (4 + 60) / -6

X1,2 = -(2) +/- akar (64) / -6

X1,2 = -(2) +/- 8 / -6

X1 = (-2 - 8) / -6 = 10/6 = 5/3

X2 = (-2 + 8) / -6 = - 1