Tìm x
1. | 7+x | = | 14x+2 |
2. | 15-8x | = | 7-4x |
3. | 6x+3 | = | x+15 |
tìm x
a(14x^3+12x^2-14x):2x=(x+2)(3x-4)
b(4x−5)(6x+1)−(8x+3)(3x−4)=15
a: ĐKXD: x<>0
\(\dfrac{14x^3+12x^2-14x}{2x}=\left(x+2\right)\left(3x-4\right)\)
=>\(\dfrac{2x\left(7x^2+6x-7\right)}{2x}=\left(x+2\right)\left(3x-4\right)\)
=>\(7x^2+6x-7=3x^2-4x+6x-8\)
=>\(7x^2+6x-7=3x^2+2x-8\)
=>\(4x^2+4x+1=0\)
=>\(\left(2x+1\right)^2=0\)
=>2x+1=0
=>x=-1/2(nhận)
b: \(\left(4x-5\right)\left(6x+1\right)-\left(8x+3\right)\left(3x-4\right)=15\)
=>\(24x^2+4x-30x-5-\left(24x^2-32x+9x-12\right)=15\)
=>\(24x^2-26x-5-24x^2+23x+12=15\)
=>-3x+7=15
=>-3x=8
=>\(x=-\dfrac{8}{3}\)
: Tìm x, biết:
a) 3x( 4x- 1) - 2x(6x- 3 )=30 b) 2x(3-2x) + 2x(2x-1)=15
c) (5x-2)(4x-1) + (10x +3)(2x - 1)=1 d) (x+2) (x+2)- (x -3)(x+1) = 9
e) (4x+1)(6x-3) = 7 + (3x – 2)(8x + 9) g) (10x+2)(4x- 1)- (8x -3)(5x+2) =14
`@` `\text {Ans}`
`\downarrow`
`a)`
`3x(4x-1) - 2x(6x-3) = 30`
`=> 12x^2 - 3x - 12x^2 + 6x = 30`
`=> 3x = 30`
`=> x = 30 \div 3`
`=> x=10`
Vậy, `x=10`
`b)`
`2x(3-2x) + 2x(2x-1) = 15`
`=> 6x- 4x^2 + 4x^2 - 2x = 15`
`=> 4x = 15`
`=> x = 15/4`
Vậy, `x=15/4`
`c)`
`(5x-2)(4x-1) + (10x+3)(2x-1) = 1`
`=> 5x(4x-1) - 2(4x-1) + 10x(2x-1) + 3(2x-1)=1`
`=> 20x^2-5x - 8x + 2 + 20x^2 - 10x +6x - 3 =1`
`=> 40x^2 -17x - 1 = 1`
`d)`
`(x+2)(x+2)-(x-3)(x+1)=9`
`=> x^2 + 2x + 2x + 4 - x^2 - x + 3x + 3=9`
`=> 6x + 7 =9`
`=> 6x = 2`
`=> x=2/6 =1/3`
Vậy, `x=1/3`
`e)`
`(4x+1)(6x-3) = 7 + (3x-2)(8x+9)`
`=> 24x^2 - 12x + 6x - 3 = 7 + (3x-2)(8x+9)`
`=> 24x^2 - 12x + 6x - 3 = 7 + 24x^2 +11x - 18`
`=> 24x^2 - 6x - 3 = 24x^2 + 18x -11`
`=> 24x^2 - 6x - 3 - 24x^2 + 18x + 11 = 0`
`=> 12x +8 = 0`
`=> 12x = -8`
`=> x= -8/12 = -2/3`
Vậy, `x=-2/3`
`g)`
`(10x+2)(4x- 1)- (8x -3)(5x+2) =14`
`=> 40x^2 - 10x + 8x - 2 - 40x^2 - 16x + 15x + 6 = 14`
`=> -3x + 4 =14`
`=> -3x = 10`
`=> x= - 10/3`
Vậy, `x=-10/3`
Bài 1:Rút gọn biểu thức
a.(x-2)(2x-1)-(2x-3)(x-1)-2
b. x(x+3y+1) -2y (x-1) - (y+x+1)x
Bài 2: Tìm x
a. (14x^3 + 12x^2 -14x) :2x = (x+2) (3x-4)
b. (4x - 5) (6x+1) - (8x+3) (3x-4) =15
Bài 1.
a)
\((x-2)(2x-1)-(2x-3)(x-1)-2\\=2x^2-x-4x+2-(2x^2-2x-3x+3)-2\\=2x^2-5x+2-(2x^2-5x+3)-2\\=2x^2-5x+2-2x^2+5x-3-2\\=(2x^2-2x^2)+(-5x+5x)+(2-3-2)\\=-3\)
b)
\(x(x+3y+1)-2y(x-1)-(y+x+1)x\\=x^2+3xy+x-2xy+2y-xy-x^2-x\\=(x^2-x^2)+(3xy-2xy-xy)+(x-x)+2y\\=2y\)
Bài 2.
a)
\((14x^3+12x^2-14x):2x=(x+2)(3x-4)\\\Leftrightarrow 14x^3:2x+12x^2:2x-14x:2x=3x^2-4x+6x-8\\ \Leftrightarrow 7x^2+6x-7=3x^2+2x-8\\\Leftrightarrow (7x^2-3x^2)+(6x-2x)+(-7+8)=0\\\Leftrightarrow 4x^2+4x+1=0\\\Leftrightarrow (2x)^2+2\cdot 2x\cdot 1+1^2=0\\\Leftrightarrow (2x+1)^2=0\\\Leftrightarrow 2x+1=0\\\Leftrightarrow 2x=-1\\\Leftrightarrow x=\frac{-1}2\)
b)
\((4x-5)(6x+1)-(8x+3)(3x-4)=15\\\Leftrightarrow 24x^2+4x-30x-5-(24x^2-32x+9x-12)=15\\\Leftrightarrow 24x^2-26x-5-(24x^2-23x-12)=15\\\Leftrightarrow 24x^2-26x-5-24x^2+23x+12=15\\\Leftrightarrow -3x+7=15\\\Leftrightarrow -3x=8\\\Leftrightarrow x=\frac{-8}3\\Toru\)
Giúp mình v
Bài10872917292872917 tìm x bt
5x-16=40+x
4x-10=15-x
-12+x=5x-2
7x-4=20+3x
5x-7=20+3x
x+15=7+6x
17-x=7-6x
3x+(-21)=12-8x
125:(3x-13)=25
541+(218-z)=735
3(2x+1)-19=14
175-5(x+3)=85
4x-40=|4|+12
x+15=20-4x
8x+|-3|=-4x+39
6(x-2)+(-2)=20-4x
5x-16=40+x
=> 5x-16-x = 40
=> 5x-x -16=40
4x-16=40
4x= 40+16
4x=56
x= 56:4
x=14
Vậy...
4x-10=15-x
=> 4x-10+x= 15
4x+x -10=15
5x= 15+10
5x= 25
x= 25:5
x=5
Vậy....
5x -16=40+x
=> 5x-x=40+16
=>4x=56
=>x=56:4
x=14
Tìm GTLN của biểu thức:
A=-x^2+6x-15
B=-2x^2+8x-15
C=-3^2+2x-1
D=-5x^2-25x+49
Tìm GTNN của biểu thức:
A=x^2-4x+7
B=x^2+8x
C=2x^2+4x+15
D=3x^2-2x-1
Tìm GTLN:
\(A=-x^2+6x-15\)
\(=-\left(x^2-6x+15\right)\)
\(=-\left(x^2-2.x.3+9+6\right)\)
\(=-\left(x+3\right)^2-6\le0\forall x\)
Dấu = xảy ra khi:
\(x-3=0\Leftrightarrow x=3\)
Vậy Amax = - 6 tại x = 3
Tìm GTNN :
\(A=x^2-4x+7\)
\(=x^2+2.x.2+4+3\)
\(=\left(x+2\right)^2+3\ge0\forall x\)
Dấu = xảy ra khi:
\(x+2=0\Leftrightarrow x=-2\)
Vậy Amin = 3 tại x = - 2
Các câu còn lại làm tương tự nhé... :)
1) 4x-(2x-5)=21
2) 14x+5=8x+10
3) 15+5x=3x+30
4) 2x-5=15-3x
5) 2(3x+5)+3(x+1)=6x+20
6) 4(x-3)+5(x-3)=18
1) 4x-(2x-5)=21
4x-2x+5=21
2x+5=21
2x=21 -5
2x=16
x=16/2
x=8
2)14x+5=8x+10
14x-8x=10-5
6x=5
x=5/6
3) 15+5x=3x+30
5x-3x=30-15
2x=15
x=15/2
Vậy x=15/2
tìm GTLN GTNN
A= x^2-4x+7
B=x^2+3x
C=2x^2+4x+15
D= x^2+6x-15
E= -2x^2+8x-15
A=x2-4x+7
= x2-4x+4+3
= (x-2)2+3
Vì (x+2)2>/ 0
Nên (x-2)2+3>/3
Vậy MAX của A=3 khi x-2=0 => x=2
Tìm x
a, (5-2x).(2x+7)-4x2+25=0
b. (5x2+3x-2)-(4x2-x-5)2=0
c.15x4-8x3-14x2-8x+15=0
GIÚP MÌNH :((
a) ( 5 - 2x )( 2x + 7 ) - 4x2 + 25 = 0
<=> ( 5 - 2x )( 2x + 7 ) + ( 5 - 2x )( 5 + 2x ) = 0
<=> ( 5 - 2x )( 2x + 7 + 5 + 2x ) = 0
<=> ( 5 - 2x )( 4x + 12 ) = 0
<=> \(\orbr{\begin{cases}5-2x=0\\4x+12=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=\frac{5}{2}\\x=-3\end{cases}}\)
b) ( 5x2 + 3x - 2 )2 - ( 4x2 - x - 5 )2 = 0 ( như này chứ nhỉ ? )
<=> [ ( 5x2 + 3x - 2 ) - ( 4x2 - x - 5 ) ][ ( 5x2 + 3x - 2 ) + ( 4x2 - x - 5 ) ] = 0
<=> ( 5x2 + 3x - 2 - 4x2 + x + 5 )( 5x2 + 3x - 2 + 4x2 - x - 5 ) = 0
<=> ( x2 + 4x + 3 )( 9x2 + 2x - 7 ) = 0
<=> ( x2 + x + 3x + 3 )( 9x2 + 9x - 7x - 7 ) = 0
<=> [ x( x + 1 ) + 3( x + 1 ) ][ 9x( x + 1 ) - 7( x + 1 ) ] = 0
<=> ( x + 1 )( x + 3 )( x + 1 )( 9x - 7 ) = 0
<=> ( x + 1 )2( x + 3 )( 9x - 7 ) = 0
<=> x + 1 = 0 hoặc x + 3 = 0 hoặc 9x - 7 = 0
<=> x = -1 hoặc x = -3 hoặc x = 7/9
c) 15x4 - 8x3 - 14x2 - 8x + 15 = 0
<=> 15x4 + 22x3 - 30x3 + 15x2 + 15x2 - 44x2 - 30x + 22x + 15 = 0
<=> ( 15x4 + 22x3 + 15x2 ) - ( 30x3 + 44x2 + 30x ) + ( 15x2 + 22x + 15 ) = 0
<=> x2( 15x2 + 22x + 15 ) - 2x( 15x2 + 22x + 15 ) + ( 15x2 + 22x + 15 ) = 0
<=> ( 15x2 + 22x + 15 )( x2 - 2x + 1 ) = 0
<=> ( 15x2 + 22x + 15 )( x - 1 )2 = 0
<=> \(\orbr{\begin{cases}15x^2+22x+15=0\\\left(x-1\right)^2=0\end{cases}}\)
+) ( x - 1 )2 = 0 <=> x = 1
+) 15x2 + 22x + 15 = 15( x2 + 22/15x + 121/225 ) + 104/15 = 15( x + 11/25 )2 + 104/15 ≥ 104/15 > 0 ∀ x
Vậy phương trình có nghiệm duy nhất là x = 1
Cảm ơn bạn câu b thiếu cái mũ 2 sorry :))
tìm x biết
a) (6x-3) (2x+4) + (4x-1) (5-3x) = -21
b) 6x (3x+5) - 2x (9x-2) + (17-x) (x-1) + x (x-18) =0
c) (15-2x) (4x+1) - (13-4x) (2x-3) - (x-1) (x+2) + x2=52
d) (8x-3) (3x+2) - (4x+7) (x+4) = (2x+1) (5x-1) - 33
Rút gọn hết ta được :
a/ 41x - 17 = -21
=> 41x = -4 => x = 4/41
b/ 34x - 17 = 0
=> 34x = 17
=> x = 17/34 = 1/2
c/ 19x + 56 = 52
=> 19x = -4
=> x = -4/19
d/ 20x2 - 16x - 34 = 10x2 + 3x - 34
=> 10x2 - 19x = 0
=> x(10x - 19) = 0
=> x = 0
hoặc 10x - 19 = 0 => 10x = 19 => x = 19/10
Vậy x = 0 ; x = 19/10
Rút gọn hết ta được :
a/ 41x - 17 = -21
=> 41x = -4 => x = 4/41
b/ 34x - 17 = 0
=> 34x = 17
=> x = 17/34 = 1/2
c/ 19x + 56 = 52
=> 19x = -4
=> x = -4/19
d/ 20x 2 - 16x - 34 = 10x 2 + 3x - 34
=> 10x 2 - 19x = 0
=> x(10x - 19) = 0
=> x = 0 hoặc 10x - 19 = 0
=> 10x = 19
=> x = 19/10
Vậy x = 0 ; x = 19/10
a) ( 6x - 3 ) ( 2x + 4 ) + ( 4x - 1 ) ( 5 - 3x ) = -21
<=> 12x2 + 24x - 6x - 12 + 20x - 12x2 - 5 + 3x = -21
<=> 41x = -21 + 12 + 5
<=> 41x = -4
<=> x = -4/41