(x) 9s2 – 4 = – 6s
Sol. 9s2 – 4 = – 6s
∴ 9s2 + 6s – 4 = 0
Comparing with as2 + bs + c = 0 we have a = 9, b = 6, c = – 4
b2 – ac = (6)2 – 4 (9) (– 4)
= 36 + 144
= 180
By Formula method,
s
|
=
|
- b ± √(b2 – 4ac)
| ||
2a
| ||||
∴ s
|
=
|
-(6) ± √180
| ||
2(9)
| ||||
∴ s
|
=
|
-6 ±√2× 2× 3× 3× 5
| ||
18
| ||||
∴ s
|
=
|
-6 ± 6√5
| ||
18
| ||||
∴ s
|
=
|
6(-1±√5)
| ||
18
| ||||
∴ s
|
=
|
-1±√5
| ||
3
| ||||
∴ s
|
=
|
-1 + √5
|
or
|
-1-√5
|
3
|
3
|
