Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
a) 4 ( x + 5 )( x + 6 )( x + 10 )( x + 12 ) = 3x2
Do x = 0 không là nghiệm pt nên chia 2 vế pt cho \(x^2\ne0\), ta được :
\(\frac{4}{x^2}\left(x^2+60+17x\right)\left(x^2+60+16x\right)=3\)
\(\Leftrightarrow4\left(x+\frac{60}{x}+17\right)\left(x+\frac{60}{x}+16\right)=3\)
Đến đây ta đặt \(x+\frac{60}{x}+16=t\left(1\right)\)
Ta được :
\(4t\left(t+1\right)=3\Leftrightarrow4t^2+4t-3=0\Leftrightarrow\left(2t+3\right)\left(2t-1\right)=0\)
Từ đó ta lắp vào ( 1 ) tính được x
1) (2x - 3)2 = 4x2 - 8
<=> 4x2 - 12x + 9 = 4x2 - 8
<=> 12x + 9 = -8
<=> 12x = -17
<=> x = 17/12
1) (2x - 3)^2 = 4x^2 - 8
<=> 4x^2 - 12x + 9 = 4x^2 - 8
<=> 4x^2 - 12x + 9 - 4x^2 = -8
<=> -12x + 9 = -8
<=> -12x = -8 - 9
<=> -12x = -17
<=> x = 17/12
2) x - (x + 2)(x - 3) = 4 - x^2
<=> x - x^2 + 3x - 2x + 6 = 4 - x^2
<=> 2x - x^2 + 6 = 4 - x^2
<=> 2x - x^2 + 6 + x^2 = 4
<=> 2x + 6 = 4
<=> 2x = 4 + 6
<=> 2x = 10
<=> x = 5
3) 3x - (x - 3)(x + 1) = 6x - x^2
<=> 3x - x^2 - x + 3x + 3 = 6x - x^2
<=> 5x - x^2 + 3 = 6x - x^2
<=> 5x - x^2 + 3 + x^2 = 6x
<=> 5x + 3 = 6x
<=> 3 = 6x - 5x
<=> 3 = x
4) 3x/4 = 6
<=> 3x = 6.4
<=> 3x = 24
<=> x = 8
5) 7 + 5x/3 = x - 2
<=> 21 + 5x = 3x - 6
<=> 5x = 3x - 6 - 21
<=> 5x = 3x - 27
<=> 5x - 3x = -27
<=> 2x = -27
<=> x = -27/2
6) x + 4 = 2/5x - 3
<=> 5x + 20 = 2x - 15
<=> 5x + 20 - 2x = -15
<=> 3x + 20 = -15
<=> 3x = -15 - 20
<=> 3x = -35
<=> x = -35/3
7) 1 + x/9 = 4/3
<=> x/9 = 4/3 - 1
<=> x/9 = 1/3
<=> x = 3
Bài làm
a) \(\frac{3x+2}{3x-2}-\frac{6}{2+3x}=\frac{9x^2}{9x-4}\)
\(\Leftrightarrow\frac{3x+2}{3x-2}-\frac{6}{3x+2}=\frac{9x^2}{\left(3x-2\right)\left(3x+2\right)}\)
\(\Leftrightarrow\frac{(3x+2)\left(3x+2\right)}{(3x-2)\left(3x+2\right)}-\frac{6\left(3x-2\right)}{(3x+2)\left(3x-2\right)}=\frac{9x^2}{\left(3x-2\right)\left(3x+2\right)}\)
\(\Rightarrow\left(3x+2\right)^2-\left(18x-12\right)=9x^2\)
\(\Leftrightarrow9x^2+12x+4-18x+12x-9x^2=0\)
\(\Leftrightarrow6x+4=0\)
\(\Leftrightarrow x=-\frac{4}{6}\)
\(\Leftrightarrow x=-\frac{2}{3}\)
Vậy x = -2/3 là nghiệm.
@Tao Ngu :))@ 9x-4 không tách thành (3x+4)(3x-4) được đâu bạn. Chỗ đó phải là: 9x2-4
Bài thiếu đkxđ của x \(\hept{\begin{cases}3x-2\ne0\\2+3x\ne0\end{cases}\Leftrightarrow\hept{\begin{cases}3x\ne2\\3x\ne-2\end{cases}\Leftrightarrow}\hept{\begin{cases}x\ne\frac{2}{3}\\x\ne\frac{-2}{3}\end{cases}\Leftrightarrow}x\ne\pm\frac{2}{3}}\)
\(a,4x-6< 7x-12\)
\(\Leftrightarrow6< 3x\Leftrightarrow x>2\)
\(b,\frac{3x-7}{4}\ge2-\frac{x+5}{3}\)
\(\Leftrightarrow3\left(3x-7\right)\ge24-4\left(x+5\right)\)
\(\Leftrightarrow13x\ge25\Leftrightarrow x\ge\frac{25}{13}\)
\(c,\frac{3x-8}{-7}\ge1-\frac{x+2}{-3}\)
\(\Leftrightarrow-3\left(3x-8\right)\ge21+7\left(x+2\right)\)
\(\Leftrightarrow-16x\ge11\)
\(\Leftrightarrow x\le-\frac{11}{16}\)
\(d,-12-8x>3+2x-\left(5-7x\right)\)
\(\Leftrightarrow14>17x\Leftrightarrow x< \frac{14}{17}\)
\(e,-1+\frac{x-1}{-3}\le\frac{x+2}{-9}\)
\(\Leftrightarrow-9-3\left(x-1\right)\le-\left(x+2\right)\)
\(\Leftrightarrow-2x\le4\Leftrightarrow x\ge-2\)
a) 7x - 35 = 0
<=> 7x = 0 + 35
<=> 7x = 35
<=> x = 5
b) 4x - x - 18 = 0
<=> 3x - 18 = 0
<=> 3x = 0 + 18
<=> 3x = 18
<=> x = 5
c) x - 6 = 8 - x
<=> x - 6 + x = 8
<=> 2x - 6 = 8
<=> 2x = 8 + 6
<=> 2x = 14
<=> x = 7
d) 48 - 5x = 39 - 2x
<=> 48 - 5x + 2x = 39
<=> 48 - 3x = 39
<=> -3x = 39 - 48
<=> -3x = -9
<=> x = 3
có bị viết nhầm thì thông cảm nha!
la`thu'hai nga`y 19 nhe
xin lỗi ,tớ nhắn nhầm.
Bài 1
a) \(7x-35=0\)
\(\Leftrightarrow7x=35\)
\(\Leftrightarrow x=5\)
b) \(4x-x-18=0\)
\(\Leftrightarrow3x=18\)
\(\Leftrightarrow x=6\)
c) \(x-6=8-x\)
\(\Leftrightarrow2x=14\)
\(\Leftrightarrow x=7\)
d)\(48-5x=39-2x\)
\(\Leftrightarrow-3x=-9\)
\(\Leftrightarrow x=3\)
Bài 2
a) \(5x-8=4x-5\)
\(\Leftrightarrow5x-4x=8-5\)
\(\Leftrightarrow1x=3\Leftrightarrow x=3\)
b) \(4-\left(x-5\right)=5\left(x-3x\right)\)
\(\Leftrightarrow4-x+5=5x-15x\)
\(\Leftrightarrow9-x=-10x\)
\(\Leftrightarrow-x+10x=-9\)
\(\Leftrightarrow9x=-9\Leftrightarrow x=-1\)
c) Chịu
d) \(2,5\left(y-1\right)=2,5y\)
\(\Leftrightarrow2,5y-2,5=2,5y\)
\(\Leftrightarrow x=\varnothing\)
Bài 3
a) \(\frac{3x-7}{5}=\frac{2x-1}{3}\)
\(\Leftrightarrow\frac{\left(3x-7\right).3}{15}=\frac{\left(2x-1\right).5}{15}\)
\(\Leftrightarrow9x-21=10x-5\)
\(\Leftrightarrow-1x=16\Leftrightarrow x=-16\)
Bài 3
b) \(\frac{4x-7}{12}-x=\frac{3x}{8}\)
\(\Leftrightarrow\frac{\left(4x-7\right).2}{24}-\frac{24x}{24}=\frac{3x.3}{24}\)
\(\Leftrightarrow8x-14-24x=9x\)
\(\Leftrightarrow-16x-14=9x\)
\(\Leftrightarrow-16x-9x=14\)
\(\Leftrightarrow-25x=14\Leftrightarrow x=\frac{-14}{25}\)
a,\(6\left(x-7\right)=5\left(x+2\right)+x\)
\(< =>6x-42=5x+10+x\)
\(< =>4x-42=6x+10\)
\(< =>-42=10\left(vo-ly\right)\)
b,\(5x-8=2\left(x-4\right)+3\)
\(< =>5x-8=2x-8+3\)
\(< =>5x=2x+3\)
\(< =>3x=3< =>x=1\)
Bài 4
a) \(\frac{5x-8}{3}=\frac{1-3x}{2}\)
\(\Leftrightarrow\frac{\left(5x-8\right).2}{6}=\frac{\left(1-3x\right).3}{6}\)
\(\Leftrightarrow10x-16=3-9x\)
\(\Leftrightarrow19x=3+16\)
\(\Leftrightarrow x=1\)
b) \(\frac{x-5}{6}-\frac{x-9}{4}=\frac{5x-3}{8}+2\)
\(\Leftrightarrow\frac{\left(x-5\right).4}{24}-\frac{\left(x-9\right).6}{24}=\frac{\left(5x-3\right).3}{24}+\frac{24.2}{24}\)
\(\Leftrightarrow4x-24-6x-54=15x-9+48\)
\(\Leftrightarrow-2x-78=15x+39\)
Đến đây thì tịt :)
\(\frac{x-5}{6}+\frac{x-9}{4}=\frac{5x-3}{8}+2\)
\(< =>\frac{\left(x-5\right).4}{24}+\frac{\left(x-9\right).6}{24}=\frac{\left(5x-3\right).3}{24}+\frac{48}{24}\)
\(< =>4x-20+6x-54=15x-9+48\)
\(< =>15x-10x=-74+39=-25\)
\(< =>5x=-25< =>x=-\frac{25}{5}=-5\)
Bài 5
a) \(6\left(x-7\right)=5\left(x+2\right)+x\)
\(\Leftrightarrow6x-42=5x+10+x\)
\(\Leftrightarrow6x-42=6x+10\)
\(\Leftrightarrow x=\varnothing\)
b) \(5x-8=2\left(x-4\right)+3\)
\(\Leftrightarrow5x-8=2x-8+3\)
\(\Leftrightarrow5x-8=2x-5\)
\(\Leftrightarrow5x-2x=8-5\)
\(\Leftrightarrow3x=3\Leftrightarrow x=1\)
\(\frac{5x-8}{3}=\frac{1-3x}{2}\)
\(< =>\left(5x-8\right).2=\left(1-3x\right).3\)
\(< =>10x-16=3-9x\)
\(< =>10x+9x=3+16\)
\(< =>19x=19\)
\(< =>x=\frac{19}{19}=1\)
\(\frac{4x-7}{12}-x=\frac{3x}{8}\)
\(< =>\frac{4x-7}{12}=\frac{3x}{8}+\frac{8x}{8}\)
\(< =>\frac{4x-7}{12}=\frac{11x}{8}\)
\(< =>\frac{\left(4x-7\right).2}{24}=\frac{11x.3}{24}\)
\(< =>8x-14=33x\)
\(< =>33x-8x=-14\)
\(< =>25x=-14\)
\(< =>x=-\frac{14}{25}\)
a) 7x - 35 = 0
<=> 7x = 0 + 35
<=> 7x = 35
<=> x = 5
b) 4x - x - 18 = 0
<=> 3x - 18 = 0
<=> 3x = 0 + 18
<=> 3x = 18
<=> x = 5
c) x - 6 = 8 - x
<=> x - 6 + x = 8
<=> 2x - 6 = 8
<=> 2x = 8 + 6
<=> 2x = 14
<=> x = 7
d) 48 - 5x = 39 - 2x
<=> 48 - 5x + 2x = 39
<=> 48 - 3x = 39
<=> -3x = 39 - 48
<=> -3x = -9
<=> x = 3
\(\frac{3x-7}{5}=\frac{2x-1}{3}\)
\(< =>\left(3x-7\right).3=\left(2x-1\right).5\)
\(< =>9x-21=10x-5\)
\(< =>9x-10x=-5+21\)
\(< =>-x=16< =>x=-16\)
c,\(32-4\left(0,5y-5\right)=3y+2\)
\(< =>32-2y+20=3y+2\)
\(< =>52-2=3y+2y\)
\(< =>5y=50\)\(< =>y=10\)
d,\(2,5\left(y-1\right)=2,5y\)
\(< =>y-1=y< =>-1=0\left(vo-ly\right)\)
a,\(5x-8=4x-5\)
\(< =>5x-4x=-5+8\)
\(< =>x=3\)
b,\(4-\left(x-5\right)=5\left(x-3x\right)\)
\(< =>4-x+5=5\left(-2x\right)\)
\(< =>-x+10x=-9\)
\(< =>9x=-9< =>x=-1\)
d,\(48-5x=39-2x\)
\(< =>48-39=-2x+5x\)
\(< =>9=3x\)\(< =>x=3\)
c,\(x-6=8-x\)
\(< =>x+x=8+6\)
\(< =>2x=14< =>x=7\)
a, \(7x-35=0\)
\(< =>7x=35\)
\(< =>x=\frac{35}{7}\)
b, \(4x-x-18=0\)
\(< =>3x=18\)
\(< =>x=\frac{18}{3}=6\)