Penjelasan dengan langkah-langkah:

pakai rumus kuadrat Gunakan rumus kuadrat

x equals the fraction with numerator negative b ± the square root of b squared minus 4 a c end root and denominator 2 a end fraction

=

−

±

2

−

4

√

2

Setelah berbentuk standar, identifikasi a, b, dan c dari persamaan awal dan masukkan ke rumus kuadrat.

x squared plus 4 x minus 21 equals 0

2

+

4

−

2

1

=

0

a equals 1

=

1

b equals 4

=

4

c equals negative 21

=

−

2

1

x equals the fraction with numerator negative 4 ± the square root of 4 squared minus 4 ⋅ 1 open paren negative 21 close paren end root and denominator 2 ⋅ 1 end fraction

=

−

4

±

4

2

−

4

⋅

1

(

−

2

1

)

√

2

⋅

1

x=-b