Ta có: \(-x^2-2x-3=-\left(x^2+2x+1+2\right)=-\left(x+1\right)^2-2\le-2< 0\forall x^{\left(đpcm\right)}\)
\(-x^2-2x-3\) < 0
⇔ -x2-2x < 3
⇔ -x( x+2) <3
⇔ -x< 3 hoặc x+2< 3
⇔ x> -3 hoặc x < 1
Tìm x biết:
a)(x+3)^2+(x-2)(x+2)-2(x+1)=7
b)x(2x-1)-(x-2)(2x+3)=0
c)(x-1)(x+2)-x-2=0
d)x[(3x+2)+(x+1)^2-(2x-5)(2x+5)]=0
đ) 2x^2-7x+5=0
e) (2x+3)(x-5)=(2x+1)(2×+3)
Bài 3
1.(x-1)(x+2)+5x-5=0
2.(3x+5)(x-3)-6x-10=0
3.(x-2)(2x+3)-7x2+14x=0
4.(x+1)(x-3)-15+5x=0
5.5(2x-1)(x+3)+5x-10x2=0
Bài4
1.3x-6+(x+1)(x-2)=0
2.4x2+6x-(2x+3)(3x-x)=0
3.5x-10-(2-x)(4+x)=0
4.10-10x+(x-1)(x-3)=0
5.20x2+30x-2(x-5)(2x+3)=0
Đề: Tìm x
a)2x.(3x+5)-x.(6x-1)=33 k)5(x+3)-2x(x+3)=0
b)x(3x-1)+12x-4=0 i)5x(x-2)-(2-x)=0
c)5x(2x+1)-12x-6=0 m)x(x-1)-2(1-x)=0
d)x3-5x2+4x-20=0
e)2x3-5x2+2x-5=0
g)(x-2)3-x(x+1).(x-1)+62=5
2/3(x22-4)=0
(x+5)2-(x+2)(x-3)=-1
x22-4+(xx-2)2=0.
2x2-6x=0
2x(x+2)-3(x+2)=0
(x+3)(x-3)+x(5-x)=-14
x(x-3)-x22+5=0
2x33+5x2-12x=0
x2-5x-24=0
x2-x-6=0
x22-6x+8=0
x3-16x=0
a) 9x2-49=0
b) (x+3)(x2-3x+9)-x(x-1)(x+1)-27=0
c) (x-1)(x+2)-x-2=0
d) x(3x+2)+(x+1)2-(2x-5)(2x+5)=0
e) (4x+1)(x-2)-(2x-3)(2x-1)=7
Em cần gấp mong mọi người giúp đỡ
Tìm x:
a) (x-20) mũ 2 -(x+1)(x+3)=-7
b) (3x+5)(4-3x)=0
c) x mũ 3 -9x=0
d)2/3x (x mũ 2 -4)=0
e) (2x+1)-x(2x+1)=0
f)(2x-1) mũ 2 -(2x+5) (2x-5) =18
g)x mũ 2 -25 =6x-9
b. x( x – 4) - 2x + 8 = 0
c. x^2-25 –( x+5 ) = 0
d.(2x -1)^2- (4x2 – 1) = 0
e. ( 3x – 1)^2 – ( x +5)^2 = 0
f. x^3 – 8 – (x -2)(x -12) =0
bài 2 tìm x
1) x^3+2x^2+2x+4=0
2) x^3+4x^2-2x-8=0
3)x^3+3x-4=0
4)x^3+x-30=0
help
Tìm x biết
a, 5x (x - 1) - (1 - x) = 0
b, (x - 3)2 - (2x + 3)2 = 0
c, 2x (x2 - 4) = 0
d, (x - 2)2 - (x - 2) (x + 3) = 6
e, x2 + 6x - 7 = 0
tìm x biết
a) 2x.(x+1) -x2.(x+2) +x3-x+4=0
b)4x. (3x+2) -6x (2x+5) +21(x-1) =0
c) 5x.(12x+7) -3x.(2x-5)=-100
d) x.(x-1) -x2+2x=5
e) 2x3.(2x-3) -x2(4x2-6x+2)=0
giúp với ạ tối nay mình phải nạp bài rồi
