a)\(\frac{5}{9}\times x-1=\frac{8}{9}\)

\(\frac{5}{9}\times x=\frac{8}{9}+1\)

\(\frac{5}{9}\times x=\frac{17}{9}\)

\(x=\frac{17}{9}:\frac{5}{9}\)

\(x=\frac{17}{5}\)

b)\(x+x\times\frac{1}{3}:\frac{2}{9}+x:\frac{2}{7}=252\)

\(x+x\times\frac{3}{2}+x:\frac{2}{7}=252\)

\(x.1+x.\frac{3}{2}+x.\frac{7}{2}=252\)

\(x\left(1+\frac{3}{2}+\frac{7}{2}\right)=252\)

\(x\times6=252\)

\(x=252:6\)

\(x=42\)

a,5/9.x-1=8/9

5/9.x=17/9

x=17/5

b,x+x.1/3:2/9+x:2/7=252

x+x.1/3.9/2+x.7/2=252

x(1+1/3.9/2+7/2)=252

x.6=252

x=42

a)\(=\dfrac{3}{3}+\dfrac{4}{3}=\dfrac{7}{3}\)

b)\(=\dfrac{5}{9}\times\dfrac{3}{2}=\dfrac{15}{18}=\dfrac{5}{6}\)

d)\(=\left(\dfrac{12}{8}-\dfrac{3}{8}\right)\times2=\dfrac{9}{8}\times2=\dfrac{18}{8}=\dfrac{9}{4}\)

c)\(=\dfrac{4}{3}-\dfrac{5}{6}=\dfrac{8}{6}-\dfrac{5}{6}=\dfrac{3}{6}=\dfrac{1}{2}\)

a) 1 + 4/3 = 7/3

b) 5/9 : 2/3 = 5/6

c ) 4/3 -1/3 x 5/2

= 1 x 5/2

= 5/2

d) ( 3/2 - 3/8) : 1/2

= 9/8 : 1/2

= 9/4

e) 15/16 : 3/8 x 3/4 

= 5/2 x 3/4

= 15/8

f) 7/19 x 1/3 x 7/19 x 2/3

= 7/19 x (1/3 x 2/3)

= 7/19 x 2/9

= 14/171

g) 3/5 x 8/27 x 25/3

= 3/5 x 25/3 x 8/27 

= 5 x 8/27

= 40/27

h) 1/5 + 4/11 + 4/5 + 7/11

= (1/5 + 4/5) + (4/11 + 7/11)

= 1 + 1

= 2

e)\(\dfrac{15}{16}\times\dfrac{8}{3}\times\dfrac{3}{4}=\dfrac{360}{192}=\dfrac{15}{8}\)

f) \(=\dfrac{7}{19}\times\left(\dfrac{1}{3}+\dfrac{2}{3}\right)=\dfrac{7}{19}\times\dfrac{3}{3}=\dfrac{7}{19}\)

g)\(=\dfrac{600}{120}=\dfrac{600:120}{120:120}=\dfrac{5}{1}=5\)

h)\(=\left(\dfrac{1}{5}+\dfrac{4}{5}\right)+\left(\dfrac{4}{11}+\dfrac{7}{11}\right)=\dfrac{5}{5}+\dfrac{11}{11}=1+1=2\)

623/12

1/15

5/12

2/7

4/15

1/4

=1/4

\(a,\dfrac{1}{3}+\dfrac{3}{4}\times\dfrac{2}{9}=\dfrac{1}{3}+\dfrac{6}{36}=\dfrac{1}{3}+\dfrac{1}{6}=\dfrac{2}{6}+\dfrac{1}{6}=\dfrac{3}{6}=\dfrac{1}{2}\)

\(b,2-\left(\dfrac{2}{5}+\dfrac{2}{3}\right)=2-\left(\dfrac{6}{15}+\dfrac{10}{15}\right)=2-\dfrac{16}{15}=\dfrac{30}{15}-\dfrac{16}{15}=\dfrac{14}{15}\)

\(c,\dfrac{2}{5}:\dfrac{4}{7}+\dfrac{1}{3}=\dfrac{2}{5}\times\dfrac{7}{4}+\dfrac{1}{3}=\dfrac{14}{20}+\dfrac{1}{3}=\dfrac{7}{10}+\dfrac{1}{3}=\dfrac{21}{30}+\dfrac{10}{30}=\dfrac{31}{30}\)

\(d,\dfrac{9}{13}:\dfrac{3}{26}-\dfrac{8}{13}=\dfrac{9}{13}\times\dfrac{26}{3}-\dfrac{8}{13}=\dfrac{234}{39}-\dfrac{8}{13}=6-\dfrac{8}{13}=\dfrac{78}{13}-\dfrac{8}{13}=\dfrac{70}{13}\)

a:=1/3+6/36

=1/3+1/6

=1/2

b: =2-16/15

=14/15

c: =2/5*7/4+1/3

=14/20+1/3

=7/10+1/3

=21/30+10/30=31/30

d: =9/13*26/3-8/13

=3-8/13=31/13

a) \(\left(2x+1\right)^2-4\left(x+2\right)^2=9\\ \Rightarrow\left[2x+1-2\left(x+2\right)\right]\left[2x+1+2\left(x+2\right)\right]=9\\ \Rightarrow\left(2x+1-2x-4\right)\left(2x+1+2x+4\right)=9\\ \Rightarrow-3\left(4x+5\right)=9\\ \Rightarrow4x+5=-3\\ \Rightarrow4x=-8\\ \Rightarrow x=-2\)

b c d nữa bạn

\(b) (x+3)^2-(x-4)(x+8)=1 <=>x^2+6x=9-(x^2+8x-4x-32)=0 \)

\(.<=> X^2+6x+9-x^2-8x+4x+32-1=0\)

\(<=>2x=-40<=>x=-20\)

=> ptrình có tập nghiêm S={-20}

c) 3(x + 2)^2 + (2x - 1)^2 - 7(x + 3)(x - 3) = 36

\(<=>3(x^2+4x+4)+(4x^2-4x+1)-7(x^2-9)=36\)

\(<=>3x^2+12x+12+4x^2-4x+1-7x^2+49=0\)

\(<=>8x=-62<=>x=7,75\)

=> ptrình có tập nghiệm S={7,75}

d)d)(x - 3)(x^2 + 3x + 9) + x(x + 2)(2 - x) = 1

\(<=> x^3+3x^2+9x-3x^2-9x-27-x(x^2-4)=1\)

\(<=>x^3+3x^2+9x-3x^2-9x-27-x^3+4x-1=0\)

\(<=> 4x=28<=> x=7\)

=> ptrình có tập nghiệm S={7}

a.\(\left(-12\right)x-14=-2\)

\(\left(-12\right)x=-2+14\)

\(\left(-12\right)x=12\)

\(x=12:\left(-12\right)\)

\(x=-1\)

\(b,\left(-8\right)x=\left(-5\right)\left(-7\right)-3\)

\(\left(-8\right)x=35-3\)

\(\left(-8\right)x=32\)

\(x=32:\left(-8\right)\)

\(x=-4\)

\(c,\left(-9\right)x+3=\left(-2\right)\left(-7\right)+16\)

\(\left(-9\right)x+3=14+16\)

\(\left(-9\right)x+3=30\)

\(\left(-9\right)x=30-3\)

\(\left(-9\right)x=27\)

\(x=27:\left(-9\right)\)

\(x=-3\)

a) 213 - 2 x X = 47

2 x X = 213 - 47

2 x X = 166

X = 166 : 2 

X = 83

b) 3 x ( X + 1 ) - 300 = 906

3 x ( X + 1 ) = 906 + 300

3 x ( X + 1 ) = 1206

X + 1 = 1206 : 3

X + 1 = 402

X = 402 - 1

X = 401

c) \(\frac{7}{3}-\frac{2}{3}\times x=\frac{1}{4}\)

\(\frac{2}{3}\times x=\frac{7}{3}-\frac{1}{4}\)

\(\frac{2}{3}\times x=\frac{25}{12}\)

\(x=\frac{25}{12}:\frac{2}{3}\)

\(x=\frac{25}{8}\)

d) \(\frac{2}{5}\times x+\frac{7}{8}=2\)

\(\frac{2}{5}\times x=2-\frac{7}{8}\)

\(\frac{2}{5}\times x=\frac{9}{8}\)

\(x=\frac{9}{8}:\frac{2}{5}\)

\(x=\frac{45}{16}\)

Học tốt #

a) \(213-2\cdot x=47\)\(\Leftrightarrow2\cdot x=166\Leftrightarrow x=83\)

b)\(3x\left(x+1\right)-300=906\Leftrightarrow3x\left(x+1\right)=606\)

\(\Leftrightarrow x\left(x+1\right)=202\Leftrightarrow x^2+x-202=0\)

\(\Leftrightarrow\left(x+\frac{1}{2}\right)^2-202,25=0\)\(\Leftrightarrow\orbr{\begin{cases}x+\frac{1}{2}=\sqrt{202,25}\\x+\frac{1}{2}=-\sqrt{202,25}\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}x=\sqrt{202,25}-0,5\\x=-\sqrt{202,25}-0,5\end{cases}}\)

a) 213 - 2*x = 47

2*x  = 213 - 47

2*x = 126

x = 63

các phần cn lại bn lm tương tự nha!
 

a: x=5:(-1/2)=-10

b: x=8/3+1/9=25/9

c: =>x+5/6=11/21

=>x=-13/42

d: =>7/4x-5=-10/3

=>7/4x=5/3

=>x=20/21

e: =>10/3-3/4:x=-1/6

=>3/4:x=10/3+1/6=21/6=7/2

=>x=3/4:7/2=3/4*2/7=6/28=3/14

g: =>3/(x+5)=3/20

=>x+5=20

=>x=15

h: =>1-1/2+1/2-1/3+...+1/x-1/x+1=49/50

=>1-1/x+1=49/50

=>x+1=50

=>x=49