cau b
(2x^2 +3x-2)/(2+x)>-1
<=>(2x^2+3x-2+x+2)/(x+2)>0
<=>[2x(x+2]/(x+2)>0
<=>x>0

Giải giúp em câu 3 ạ

bai 2
x^2-2mx-3m+4=0
co nghiem pb thoa man P= x1^2+x2^2+x1x2=3
....
delra =m^2 +3m-4=(m-1)(m+4)
delta>0; m <-4; hoac m >1
vivet
x1+x2=2m
x1.x2=-3m+4
P=(x1+x2)^2-x1.x2
P=4m^2 +3m-4
P=3<=>4m^2+3m-7=0
(m-1)(4m+7)=0
m=1(l)
m=-7/4 (l)
vo nghiem

cau 3
tana =3
S=(2sin^3a +cosa.sin^2a +cosa)/(sina-2cos^3a)
cosa#0
chia cos^3a; tana =t; 1/cos^2a =t^2+1
S=[2t^3 +t^2+(t^2+1)]/[(t^2+1)-2]
S=(2t^3+2t^2 +1)/(t^2-1
S=(54+18+1)/(9-1)=73/8

cau 4
A(1;2); B(2;-3);C(3;5)
...
a)
BC (1;8) ;
AH(8;-1)
ptdtqua A vuong BC
(x-1)+8(y-2)=0
x+8y-17=0

b)
A(1;2); B(2;-3);C(3;5)
pt dtr tam B tiepbxuc AC
AC: (2;3)
AC ; 3(x-1)-2(y-2)=3x-2y+1=0
R =(|3.2+2.3+1|/√(9+4)
R^2=13
ptdr tam B bk R
(c) : (x-2)^2 +(y+3)^2=13

cau4
c)
A(1;2); B(2;-3);C(3;5)
AB(1;-5)
dt qua AB : 5(x-1)+(y-2)=5x+y-7=0
∆ : x-5y +m=0
M(0;m/5)
N(-m;0)
O(0;0)
S∆M />OM. />|m/5.m|=20
m=+-10
∆: x-5y±10