13=(7X-33) :12
[(7X-31):5]*36= 7236
1+2+3+4+5+...+100+X =5350
80-9(X -4) =35
(3X-21):4+108=114
[(6X-72):2-84]*14=2814
28x+12x=80
249-7(1+x)=200
20-[(x-5)*7 +4]=2
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20) -5-(x + 3) = 2 - 5x ⇔ -5 - x - 3 = 2 -5x ⇔ 4x = 10 ⇔ x = \(\frac{5}{2}\)
Vậy...
1: \(\dfrac{4}{23}+\dfrac{5}{21}+\dfrac{1}{2}-\dfrac{4}{23}+\dfrac{16}{21}\)
\(=1+\dfrac{1}{2}\)
\(=\dfrac{3}{2}\)
2: \(\left(\dfrac{1}{3}+\dfrac{12}{67}+\dfrac{13}{41}\right)-\left(\dfrac{79}{67}-\dfrac{28}{41}\right)\)
\(=\dfrac{1}{3}+\dfrac{12}{67}+\dfrac{13}{41}-\dfrac{79}{67}+\dfrac{28}{41}\)
\(=\dfrac{1}{3}\)
Mấy cái này chuyển vế đổi dấu là xong í mà :3
1,
16-8x=0
=>16=8x
=>x=16/8=2
2,
7x+14=0
=>7x=-14
=>x=-2
3,
5-2x=0
=>5=2x
=>x=5/2
Mk làm 3 cau làm mẫu thôi
Lúc đăng đừng đăng như v :>
chi ra khỏi ngt nản
từ câu 1 đến câu 8 cs thể làm rất dễ,bn tham khảo bài của bn muwaa r làm những câu cn lại
1: \(=6x^2+2x-15x-5-x^2+6x-9+4x^2+20x+25-27x^3-27x^2-9x-1\)
=-27x^3-18x^2+4x+10
2: =4x^2-1-6x^2-9x+4x+6-x^3+3x^2-3x+1+8x^3+36x^2+54x+27
=7x^3+37x^2+46x+33
5:
\(=25x^2-1-x^3-27-4x^2-16x-16-9x^2+24x-16+\left(2x-5\right)^3\)
\(=8x^3-60x^2+150-125+12x^2-x^3+8x-60\)
=7x^3-48x^2+8x-35
\(\left(4-3x\right)\left(10x-5\right)=0\)
\(\Rightarrow\orbr{\begin{cases}4-3x=0\\10x-5=0\end{cases}\Rightarrow\orbr{\begin{cases}3x=4\\10x=5\end{cases}\Rightarrow}\orbr{\begin{cases}x=\frac{4}{3}\\x=\frac{1}{2}\end{cases}}}\)
\(\left(7-2x\right)\left(4+8x\right)=0\)
\(\Rightarrow\orbr{\begin{cases}7-2x=0\\4+8x=0\end{cases}\Rightarrow\orbr{\begin{cases}2x=7\\8x=-4\end{cases}\Rightarrow\orbr{\begin{cases}x=\frac{7}{2}\\x=-\frac{1}{2}\end{cases}}}}\)
rồi thực hiện đến hết ...
Brainchild bé ngây thơ qus e , ko thực hiện đến hết như thế đc đâu :>
\(\left(x-3\right)\left(2x-1\right)=\left(2x-1\right)\left(2x+3\right)\)
\(2x^2-7x+3=4x^2+4x-3\)
\(2x^2-7x+3-4x^2-4x+3=0\)
\(-2x^2-11x+6=0\)
\(2x^2+11x-6=0\)
\(2x^2+12x-x-6=0\)
\(2x\left(x+6\right)-\left(x+6\right)=0\)
\(\left(x+6\right)\left(2x-1\right)=0\)
\(x+6=0\Leftrightarrow x=-6\)
\(2x-1=0\Leftrightarrow2x=1\Leftrightarrow x=\frac{1}{2}\)
\(3x-2x^2=0\)
\(x\left(2x-3\right)=0\)
\(x=0\)
\(2x-3=0\Leftrightarrow2x=3\Leftrightarrow x=\frac{3}{2}\)
Tự lm tiếp nha
a) \(3x-18.28:14=308\)
\(=>3x-36=308\)
\(=>3x=344\)\(\)
\(=>x=\frac{344}{3}\)
\(\)b)\(38+\left|x\right|=\left(-12\right)+65\)
\(=>38+\left|x\right|=53=>\left|x\right|=15=>\orbr{\begin{cases}x=15\\x=-15\end{cases}}\)
c)\(15+3.\left(x-1\right):5=30\)
\(=>15+3.\left(x-1\right)=150\)
\(=>3.\left(x-1\right)=135\)
\(x-1=45=>x=46\)
d) \(5.\left(7-3x\right)+7.\left(2+2x\right)=1\)
\(=>35-15x+14+14x=1\)
\(=>49-x=1=>x=48\)
e)\(3.\left(x-7\right)=21\)
\(=>x-7=7=>x=14\)
g)\(\left[\left(6x-72\right):2-84\right]:28=5628\)
\(\left(6x-72\right):2-84=157584\)
\(\left(6x-72\right):2=157668\)
\(6x-72=315336\)
\(6x=315408=>x=52568\)
h)\(123-5\left(x+4\right)=28\)
\(5.\left(x+4\right)=95\)
\(x+4=19=>x=15\)
p)\(14.\left(x-3\right)-138=73\)
\(14.\left(x-3\right)=211\)
\(x-3=\frac{211}{14}=>x=\frac{253}{14}\)
\(t\)
\(\left|x\right|-5=2\)
\(\left|x\right|=7=>\orbr{\begin{cases}x=7\\x=-7\end{cases}}\)
v)\(4x-72=\left|100-8.25\right|\)
\(4x-72=\left|-100\right|\)
\(4x-72=100=>4x=172=>x=43\)
cậu có thể tham khảo bài làm trên đây ạ, chúc cậu học tốt ^^
Bài 1:
a) \(-5\left(x^2-3x+1\right)+x\left(1+5x\right)=x-2\)
\(\Rightarrow-5x^2+15x-5+x+5x^2=x-2\)
\(\Rightarrow16x-5=x-2\)
\(\Rightarrow16x-x=5-2\)
\(\Rightarrow15x=3\)
\(\Rightarrow x=\dfrac{15}{3}=5\)
b) \(12x^2-4x\left(3x+5\right)=10x-17\)
\(\Rightarrow12x^2-12x^2-20x=10x-17\)
\(\Rightarrow-20x=10x-17\)
\(\Rightarrow-20x-10x=-17\)
\(\Rightarrow-30x=-17\)
\(\Rightarrow x=\dfrac{-30}{-17}=\dfrac{30}{17}\)
c) \(-4x\left(x-5\right)+7x\left(x-4\right)-3x^2=12\)
\(\Rightarrow-4x^2+20x+7x^2-28x-3x^2=12\)
\(\Rightarrow-8x=12\)
\(\Rightarrow x=\dfrac{12}{-8}=-\dfrac{4}{3}\)
Bài 2:
a) \(\left(x+5\right)\left(x-7\right)-7x\left(x-3\right)\)
\(=x^2-7x+5x-35-7x^2+21x\)
\(=-6x^2+19x-35\)
b) \(x\left(x^2-x-2\right)-\left(x-5\right)\left(x+1\right)\)
\(=x^3-x^2-2x-x^2+x-5x-5\)
\(=x^3-2x^2-6x-5\)
c) \(\left(x-5\right)\left(x-7\right)-\left(x+4\right)\left(x-3\right)\)
\(=x^2-7x-5x+35-x^2-3x+4x-12\)
\(=11x+23\)
d) \(\left(x-1\right)\left(x-2\right)-\left(x+5\right)\left(x+2\right)\)
\(=x^2-2x-x+2-x^2+2x+5x+10\)
\(=4x+12\)
18x -19 = 21 + 8x
18 x - 8x = 21 + 19
10 x = 40
x =4
g) 18 -4x=-20-6x
-4x + 6x = -20 - 18
2x = -38
x= -19
k, -10 \(x\) - 27 = -7\(x\) + 33
-27 - 33 = -7\(x\) + 10\(x\)
3\(x\) = -60
\(x\) - 20
m, -17\(x\) - 24 = -9\(x\) - 40
-24 + 40 = -9\(x\) + 17\(x\)
8\(x\) = 16
\(x\) = 2
chuyển đổi lại : (7x - 3) : 12 = 13
=> (7x - 3) = 13 * 12
=> 7x - 3 = 156
=> 7x = 159
=> x= 159/7
[(7x - 31) : 5] * 36 = 7236
=> [(7x - 31) : 5] = 7236 : 36 = 201
=> (7x - 31) : 5 = 201
=> 7x - 31 = 1005
=> 7x = 1036
=> x = 148
1 + 2 + 3 + 4 + 5 +... + 100 + x = 5350
SSH : \(\left(100-1\right):1+1=100\)
=> tổng : \(\frac{\left(1+100\right)\cdot100}{2}=5050\)
=> 5050 + x = 5350
=> x = 5350 - 5050 = 300
80 - 9(x - 4) = 35
=> 9(x - 4) = 80 - 35 = 45
=> x - 4 = 45 : 9
=> x - 4 = 5
=> x = 9
(3x - 21) : 4 + 108 = 114
=> (3x - 21) : 4 = 114 - 108 = 6
=> 3x - 21 = 24
=> 3x = 45
=> x = 15
[(6x - 72) : 2 - 84]*14 = 2814
=> [(6x - 72) : 2 - 84] = 201
=> (6x - 72) : 2 - 84 = 201
=> (6x - 72) : 2 = 285
=> 6x - 72 = 570
=> 6x = 642
=> x = 107
28x + 12x = 80
=> 40x = 80
=> x = 2
249 - 7(1 + x) = 200
=> 7(1 + x) = 49
=> 1 + x = 7
=> x = 6
20 - [(x - 5) * 7 + 4] = 2
=> [(x - 5) * 7 + 4] = 18
=> (x - 5)*7 + 4 = 18
=> (x - 5) * 7 = 14
=> x - 5 = 2
=> x = 7
\(\frac{7x-33}{12}=13\)
\(7x-33=13\cdot12\)
\(7x-33=156\)
\(7x=156+33\)
\(7x=189\)
\(x=\frac{189}{7}=27\)
\(\frac{7x-31}{5}\cdot36=7236\)
\(\frac{7x-31}{5}=\frac{7236}{36}\)
\(\frac{7x-31}{5}=201\)
\(7x-31=201\cdot5\)
\(7x-31=1005\)
\(7x=1005+31\)
\(7x=1036\)
\(x=\frac{1036}{7}=148\)
\(1+2+3+4+5+..+100+x=5350\)
\(\left(1+2+3+4+5+...+100\right)+x=5350\)
Phần 1 + 2 + 3 + 4 + 5 + ... + 100 có số số hạng là :
\(\frac{100-1}{1}+1=100\) ( số hạng )
\(\Rightarrow\frac{\left(100+1\right)\cdot100}{2}+x=5350\)
\(5050+x=5350\)
\(x=5350-5050=300\)
\(80-9\left(x-4\right)=35\)
\(9\left(x-4\right)=80-35\)
\(9\left(x-4\right)=45\)
\(x-4=\frac{45}{9}\)
\(x-4=5\)
\(x=5+4=9\)
\(\frac{3x-21}{4}+108=114\)
\(\frac{3x-21}{4}=114-108\)
\(\frac{3x-21}{4}=6\)
\(3x-21=6\cdot4\)
\(3x-21=24\)
\(3x=24+21\)
\(3x=45\)
\(x=\frac{45}{3}=15\)
\(14\left(\frac{6x-72}{2}-84\right)=2814\)
\(3x-36-84=\frac{2814}{14}\)
\(3x-120=201\)
\(3x=201+120\)
\(3x=321\)
\(x=\frac{321}{3}=107\)
\(28x+12x=80\)
\(x\left(28+12\right)=80\)
\(x\cdot40=80\)
\(x=\frac{80}{40}=2\)
\(249-7\left(1+x\right)=200\)
\(-7\left(1+x\right)=200-249\)
\(-7\left(1+x\right)=-49\)
\(1+x=\frac{-49}{-7}\)
\(1+x=7\)
\(x=7-1=6\)
\(20-7\left(x-5\right)+4=2\)
\(20-7\left(x-5\right)=2-4\)
\(20-7\left(x-5\right)=-2\)
\(-7\left(x-5\right)=-2-20\)
\(-7\left(x-5\right)=-22\)
\(x-5=\frac{-22}{-7}\)
\(x=\frac{22}{7}+5=\frac{57}{7}\)