急!!!thx~中四maths~solving equations! (10points)

a) Let a= x^2
a^2-3a-4=0
a=-1, 4
so x^2=-1(rej), x^2=4------=±2

b)x-4=2x
x=-4

c)x-1=x^2-6x+9
0=x^2-7x+10
x=2,5

d)Let a= x+1
just like a)

e)In x+y-3=0,
x=3-y----------------(1)
put(1) into y=x^2-2x-3
y=(3-y)^2-2(3-y)-3
y=2,3
put y=2,3 into (1)
x=1,0
so the answers are(1,2), (3,0)

f){3x^2+2y+1=0----------------(1)
　{ 3y-4x=41--------------------(2)
in(2)
y=(41+4x)÷3--------(3)
(3)-->(1)
....so on
h) x+2x=6
x=2

a)x^4-3x^2-4=0

Let y=x^2 if y<0 then there is no solution

(b)x-4/x=2

let x do not equal zero then X-4=2X

(c)開方x-1=x-3

爆開個開方佢

(d)(x+1)^2-4(x+1)-5=0

方法一爆開２次方
方法二ｌｅｔ　y=x+1 計完要ｙ的值要－１

(e) { y=x^2-2x-3
　 {x+y-3=0

用第二條公式代ｙ＝ｘｘ入第一條式
有機會有二個答案一個答案以及零個答案

(f) {3x^2+2y+1=0
　{ 3y-4x=41
同ｅ一樣

(g)3/x+1 + x+1/x+3 = 8/x^2+2x-3
二邊乘（ｘ＋１）（ｘ＋３）ｘ＾２　不過呢個係四次方方程
如果係中四有機會好似ａ　咁樣ｌｅｔ　ｙ＝ｘ＾２

(h)x + 2x/x-3 =6/x-3
二邊乘（ｘ－３）就計到



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