bài 15 :tìm x∈Q, biết.
a) ( x - 3).( x +4 ) > 0 b)( x + 2).( x - 5) < 0
Bài 4: Tìm x, biết.
a) 4x(x - 7) - 4x2 = 56
b) 12x(3x - 2) - (4 - 6x) = 0
c) 4(x - 5) - (5 - x)2 = 0
d) x(x +1) - x(x - 3) = 0
e) - 6x + 8 = 0 f) 2 + 2x + = 0
c: \(\Leftrightarrow\left(x-5\right)\left(x+1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=5\\x=-1\end{matrix}\right.\)
Tìm x thuộc z,biết.a,-4[x-5] bé hơn 0.b,[x-2][x-6]bé hơn 0
\(a.-4\left(x-5\right)< 0\)
\(\Leftrightarrow x-5>0\)
\(\Leftrightarrow x>5\)
\(b.\left(x-2\right)\left(x-6\right)< 0\)
\(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x-2>0\\x-6< 0\end{matrix}\right.\\\left\{{}\begin{matrix}x-2< 0\\x-6>0\end{matrix}\right.\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}2< x< 6\left(n\right)\\6< x< 2\left(l\right)\end{matrix}\right.\)
a) Ta có: \(-4\cdot\left(x-5\right)< 0\)
\(\Leftrightarrow-4\) và x-5 khác dấu
mà -4<0
nên x-5>0
hay x>5
Vậy: x>5
b) Ta có: \(\left(x-2\right)\left(x-6\right)< 0\)
\(\Leftrightarrow x-2;x-6\) khác dấu
Trường hợp 1:
\(\left\{{}\begin{matrix}x-2>0\\x-6< 0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x>2\\x< 6\end{matrix}\right.\Leftrightarrow2< x< 6\)
Trường hợp 2:
\(\left\{{}\begin{matrix}x-2< 0\\x-6>0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x< 2\\x>6\end{matrix}\right.\Leftrightarrow x\in\varnothing\)
Vậy: 2<x<6
Tìm x, biết.
a/ 3x + 2(5 – x) = 0 b/ x(2x – 1)(x + 5) – (2x2 + 1)(x + 4,5) = 3,5
c/ 3x2 – 3x(x – 2) = 36.
d/ (3x2 – x + 1)(x – 1) + x2(4 – 3x) =
Bài 1: Tính chia:
a) (6x5y2 - 9x4y3 + 15x3y4): 3x3y2 b) (2x3 - 21x2 + 67x - 60): (x - 5)
c) (6x3 – 7x2 – x + 2) : (2x + 1) d) (x2 – y2 + 6x + 9) : (x + y + 3)
a: =>3x+10-2x=0
hay x=-10
c: \(\Leftrightarrow3x^2-3x^2+6x=36\)
=>6x=36
hay x=6
Bài1: Thực hiện phép tính
a) 2x(3x2 – 5x + 3) b) - 2x ( x2 + 5x+3)
Bài 4: Tìm x, biết.
a/ 3x + 2(5 – x) = 0 b/ x(2x – 1)(x + 5) – (2x2 + 1)(x + 4,5) = 3,5
c/ 3x2 – 3x(x – 2) = 36.
II. PHÂN TÍCH ĐA THỨC THÀNH NHÂN TỬ
Bài1: Phân tích đa thức thành nhân tử.
a/ 14x2y – 21xy2 + 28x2y2 b/ x(x + y) – 5x – 5y.
c/ 10x(x – y) – 8(y – x). d/ (3x + 1)2 – (x + 1)2
e/ 5x2 – 10xy + 5y2 – 20z2. f/ x2 + 7x – 8
g/ x3 – x + 3x2y + 3xy2 + y3 – y h/ x2 + 4x + 3.
Bài 1:
a: \(=6x^3-10x^2+6x\)
b: \(=-2x^3-10x^2-6x\)
Bài 4:
a: =>3x+10-2x=0
=>x=-10
c: =>3x2-3x2+6x=36
=>6x=36
hay x=6
Bài 1:
\(a,=6x^3-10x^2+6x\\ b,=-2x^3-10x^2-6x\)
Bài 4:
\(a,\Leftrightarrow3x+10-2x=0\Leftrightarrow x=-10\\ b,\Leftrightarrow x\left(2x^2+9x-5\right)-\left(2x^3+9x^2+x+4,5\right)=3,5\\ \Leftrightarrow2x^3+9x^2-5x-2x^3-9x^2-x-4,5=3,5\\ \Leftrightarrow-6x=8\Leftrightarrow x=-\dfrac{4}{3}\\ c,\Leftrightarrow3x^2-3x^2+6x=36\Leftrightarrow x=6\)
Bài 1:
\(a,=7xy\left(2x-3y+4xy\right)\\ b,=x\left(x+y\right)-5\left(x+y\right)=\left(x-5\right)\left(x+y\right)\\ c,=\left(x-y\right)\left(10x+8\right)=2\left(5x+4\right)\left(x-y\right)\\ d,=\left(3x+1-x-1\right)\left(3x+1+x+1\right)\\ =2x\left(4x+2\right)=4x\left(2x+1\right)\\ e,=5\left[\left(x-y\right)^2-4z^2\right]=5\left(x-y-2z\right)\left(x-y+2z\right)\\ f,=x^2+8x-x-8=\left(x+8\right)\left(x-1\right)\\ g,\left(x+y\right)^3-\left(x+y\right)=\left(x+y\right)\left[\left(x+y\right)^2-1\right]\\ =\left(x+y\right)\left(x+y-1\right)\left(x+y+1\right)\\ h,=x^2+3x+x+3=\left(x+3\right)\left(x+1\right)\)
Tìm x, y ∈ Z biết.
a) (x + 1)(y – 2) = 0
b) (x – 5)(y – 7) = 1
c) (x + 4)(y – 2) = 2
d) (x + 3)(y – 6) = -4
e) (x + 7)(5 – y) = -6
f) (12 – x)(6 – y) = -2
bài 15 :tìm \(x\)ϵQ, biết
a) ( x - 3).( x +4 ) > 0 b)( x + 2).( x - 5) < 0
a: \(\Leftrightarrow\left[{}\begin{matrix}x>3\\x< -4\end{matrix}\right.\)
Ae nào giúp mik giải những bài này đc ko ?
Bài 1:Tìm
1/ Ước(10) và B(10)
2/Ước(+15) và B(+15)
3/Ước(-24) và B(-24)
4/Ước chung(12;18)
5/Ước chung(-15;+20)
Bài 2:Tìm x
1/x.(x+7)=0
2/(x+12).(x-3)=0
3/(-x +5).(3-x)=0
4/x.(2+x).(7-x)=0
5/(x-1).(x+2).(-x -3)=0
Giúp mik nha
Dễ mak
nhưng mik nhìn đề thấy dài quá nên ko muốn làm
hihi^_$
Trả lời :
k bình luận linh tinh nx
~HT~
Tìm x biết.
a)(x+2)3-x2(x+6)=0
b) (2x+3)3-8x(x-1)(x+1)=9x(4x-3)
c)(2-x)3+(2+x)3-12x(x+1)=0
a) \(\left(x+2\right)^3-x^2\left(x+6\right)=0\)
\(\Leftrightarrow x^3+6x^2+12x+8-x^3-6x^2=0\)
\(\Leftrightarrow12x+8=0\)
\(\Leftrightarrow12x=-8\)
\(\Leftrightarrow x=-\dfrac{8}{12}\)
\(\Leftrightarrow x=-\dfrac{2}{3}\)
b) \(\left(2x+3\right)^3-8x\left(x+1\right)\left(x-1\right)=9x\left(4x-3\right)\)
\(\Leftrightarrow8x^3+36x^2+54x+27-8x\left(x^2-1\right)=36x^2-27x\)
\(\Leftrightarrow8x^3+36x^2+54x+27-8x^3+8x=36x^2-27x\)
\(\Leftrightarrow8x^3-8x^3+36x^2-36x^2+54x+27x+8x+27=0\)
\(\Leftrightarrow89x+27=0\)
\(\Leftrightarrow x=-\dfrac{27}{89}\)
c) \(\left(2-x\right)^3+\left(2+x\right)^3-12x\left(x+1\right)=0\)
\(\Leftrightarrow8-12x+6x^2-x^3+8+12x+6x^2+x^3-12x^2-12x=0\)
\(\Leftrightarrow\left(x^3-x^3\right)+\left(6x^2+6x^2-12x^2\right)-\left(12x-12x\right)+12x+\left(8+8\right)=0\)
\(\Leftrightarrow12x+16=0\)
\(\Leftrightarrow x=-\dfrac{16}{12}\)
\(\Leftrightarrow x=-\dfrac{4}{3}\)
`#040911`
`a)`
`(x + 2)^3 - x^2(x + 6) = 0`
`<=> x^3 + 6x^2 + 12x + 8 - x^3 - 6x^2 = 0`
`<=> (x^3 - x^3) + (6x^2 - 6x^2) + 12x = 0`
`<=> 12x = 0`
`<=> x = 0`
Vậy, `x = 0.`
`b)`
`(2x + 3)^3 - 8x(x - 1)(x + 1) = 9x(4x - 3)`
`<=> 8x^3 + 36x^2 + 54x + 27 - 8x(x^2 - 1) = 36x^2 - 27x`
`<=> 8x^3 + 36x^2 + 54x + 27 - 8x^3 + 8x - 36x^2 + 27x = 0`
`<=> (8x^3 - 8x^3) + (36x^2 - 36x^2) + (54x + 8x + 27x) + 27 = 0`
`<=> 89x + 27 = 0`
`<=> 89x = -27`
`<=> x = -27/89`
Vậy, `x = -27/89`
`c)`
`(2 - x)^3 + (2 + x)^3 - 12x(x + 1) = 0`
`<=> 8 - 12x + 6x^2 - x^3 + 8 + 12x + 6x^2 + x^3 - 12x^2 - 12x = 0`
`<=> (-x^3 + x^3) + (12x - 12x - 12x) + (6x^2 + 6x^2 - 12x^2) + (8 + 8)=0`
`<=> -12x + 16 = 0`
`<=> -12x = -16`
`<=> 12x = 16`
`<=> x=4/3`
Vậy, `x = 4/3.`
Bài 13: Tìm x biết: a) (x-2)(x-3)-D0. b) (x-3)(x-4)-0. c) (x-7)(6-x)=0. d) (x-3)(x-13)=0. The Bài 14: Tìm x biết: a) (12-x)(2-x)=0. b) (x-33)(11-x)=0. c) (21-x)(12-x)=0. d) (50-x)(x-150) =0. Bài 15: Tìm x biết: a) 2x +x = 45. b) 2x +7x = 918. c) 2x+3x 60+5. d) 11x+22x 33.2.