Math Algebra Questions..Help

我用 ^ 代表乘方

1. y^2 + 4y -1 =0 ( )=square
y^2 + 4y + 4 – 5 = 0
(y + 2)^2 – (√5)^2 = 0
[(y + 2) + √5][(y + 2) - √5] = 0
(y + 2 + √5)(y + 2 - √5) = 0
y = - (2 + √5)
或
y = √5 - 2

2. (a-2) (a+1)= 3a^2 – 4
(a-2) (a+1)= 3a^2 – 4
a^2 – a – 2 = 3a^2 – 4
2a^2 + a – 2 = 0
a^2 + a/2 – 1 = 0
a^2 + a/2 + (1/4)^2 – (1/4)^2 – 1 = 0
(a + 1/4)^2 –√(17/16)^2= 0
[(a + 1/4) + √(17/16)][(a + 1/4) - √(17/16)] = 0
a = - (1 + √17)/4
或
a = (√17 - 1)/4

3. √(3X)= 2+ √(X+ 4)
3X = 4 + 4√(X+ 4) + X+4
2X – 8 = 4√(X+ 4)
X – 4= 2√(X+ 4)
(X – 4)^2= (2√(X+ 4))^2
X^2 – 8X + 16 = 4X + 16
X^2 – 12X = 0
X(X – 12) = 0
X = 0 (不合)
或
X = 12