Penjelasan dengan langkah-langkah:

7x² + bx – 2 = 0

salah satu akarnya x = -2

7(-2)² + b(-2) – 2 = 0

28 – 2b – 2 = 0

2b = 28 – 2

2b = 26

b = 13

7x² + 13x – 2 = 0

( 7x – 1 )(x + 2) = 0

(x + 2) = 0

x = – 2

(7x – 1) = 0

x = 1/7

jadi nilai b = 13, akar lainnya x = 1/7