Question

URGENT!!! Find the positive root of whole root of (3x2 + 6) = 9(not under root) .

Answer 1

√3x²+6 = 9----(1)
do the square of (1)
3x² +6 = 81
3x² = 81-6
3x²=75
x² =75/3
x² =25
x =+ or -√25
x= 5 or x= -5
∴ we need positive x 
x=5

Answer 2

√(3x²+6) = 9

take square both sides

3x² +6 = (9)² = 81

3x² = 81 -6 = 75

x² = 75/3 = 25

x² = (5)²

x² -5² =0

use formula,
a² -b² = (a -b)(a + b)

now ,

(x +5)(x -5) =0

x = ± 5

hence, x = 5 and -5