equation problem

65.(a) u = √(2x + 3)
u^2 = 2x + 3
x = (u^2 - 3)/2
5√(2x + 3) - 7 = 6x
5u - 7 = 6(u^2 - 3)/2
5u - 7 = 3u^2 - 9
3u^2 - 5u - 2 = 0
(b) 5√(2x + 3) - 7 = 6x
3u^2 - 5u - 2 = 0
(u - 2)(3u + 1) = 0
u = 2 or u = -1/3
√(2x + 3) = 2 or √(2x + 3) = -1/3
2x + 3 = 4 or 2x + 3 = 1/9
x = 1/2 or x = -13/9(rejected after checking)

67(a) x^2 + x - 2x√(x + 4) = 60
x^2 + x - 2x√(x + 4) + 4 = 64
x^2 - 2x√(x + 4) + √(x + 4)^2 = 64
[x - √(x + 4)]^2 = 64

(b) x^2 + x - 2x√(x + 4) = 60
[x - √(x + 4)]^2 = 64
x - √(x + 4) = 8 or x - √(x + 4) = -8
x - 8 = √(x + 4) or x + 8 = √(x + 4)
x^2 - 16x + 64 = x + 4 or x^2 + 16x + 64 = x + 4
x^2 - 17x + 60 = 0 or x^2 + 15x + 60 = 0 (rejected for no solution)
Hence x^2 - 17x + 60 = 0
(x - 12)(x - 5) = 0
x = 12 or x = 5(rejected after checking)