Tìm x biết:9/10-x=1/3
tìm x biết (x+1)/10 + (x+2)/9 +(x+3)/8 = -3
Từ đề bài=>(x+1)/10+(x+2)/9+(x+3)/8-(-3)=0
<=>......................................(như trên)+3=0
<=>(x+1)/10+1+(x+2)/9+1+(x+3)/8+1=0( vì 1+1+1=3)
<=>(x+1+10)/10+(x+2+9)/9+(x+3+8)/8=0
<=>(x+11)/10+(x+11)/9+(x+11)/8=0
<=>(x+11).(1/10+1/9+1/8)=0
Mà 1/10<1/9<1/8
=>1/10+1/9+1/8 khác 0
<=>x+11=0<=>x=-11
Vậy x=-11
Câu 1: Tìm x,y,z biết 2x/3=3y/4=4z/5 và x-2y+3z=-31
Câu 2: Tìm x biết x-6/7+x-7/8+x-8/9=x-9/10+x-10/11+x-11/12
Câu 3: A =1/15+1/16+1/17+...+1/44
CMR: A>5/6
Tìm x biết: (x-3)+(x-2)+(x-1)+...+9+10+11=11
tìm x biết (x + 1) + (x + 2) + (x + 3) + ... + (x + 9) + (x + 10) = 85
( x+1) + (x+2) +( x+3) +...+( x+9)+(x+10) = 85
\(x+1+x+2+x+3+...+x+9+x+10=85\)
\(10\times x+\left(1+2+3+...+9+10\right)=85\)
\(10\times x+\left[\left(1+10\right)\times10:2\right]=85\)
\(10\times x+55=85\)
\(10\times x=85-55\)
\(10\times x=30\)
\(x=30:10\)
\(x=3\)
( x + 1 ) + ( x + 2 ) + ( x + 3 ) + .......... + ( x + 9 ) + ( x + 10) = 85
x . 10 + ( 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 ) = 85
x . 10 + 55 = 85
x . 10 = 85 - 55
x . 10 = 30
x = 30 : 10
x = 3
Vậy x = 3
(x + 1) + (x + 2) + (x + 3) + ... + (x + 9) + (x + 10) = 85
x * 10 + ( 1 + 2 +3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 ) = 85
x * 10 + 55 = 85
x * 10 = 85 - 55
x * 10 = 30
x = 30 : 10
x = 3
bài 1:Tìm x biết
a,X x 3/4 = 9/14 b,x : 5/9 = 3/10
bài 2:Tính
a, 3/10 + 2/5 : 4/15 b, 4/7 x 3 + 2/3 x 2
Giúp mình với nhé
Bài 1:
a) \(x.\dfrac{3}{4}=\dfrac{9}{14}\)
\(\Rightarrow x=\dfrac{9}{14}:\dfrac{3}{4}\)
\(\Rightarrow x=\dfrac{6}{7}\)
b) \(x:\dfrac{5}{9}=\dfrac{3}{10}\)
\(\Rightarrow x=\dfrac{3}{10}.\dfrac{5}{9}\)
\(\Rightarrow x=\dfrac{1}{6}\)
Bài 2:
a) \(\dfrac{3}{10}+\dfrac{2}{5}:\dfrac{4}{15}=\dfrac{3}{10}+\dfrac{3}{2}=\dfrac{9}{5}\)
b) \(\dfrac{4}{7}.3+\dfrac{2}{3}.2=\dfrac{12}{7}+\dfrac{4}{3}=\dfrac{64}{21}\)
tìm x biết:( x+1) + ( x+ 2) + ( x+3)+ ( x+4)+.....+( x+9)+ ( x+10) = 2015
khoan cach giua 2 so la :2-1=1
co tat ca so so hang hay x la :(10-1):1+1=10
(x+1)+(x+2)+.....................(x+10)=2015
x*10+[(1+10)*10/2]=2015
x*10+55 =2015
x*10 =2015-55
x*10 =1960
x =1960/10
x =196
tìm x biết:( x+1) + ( x+ 2) + ( x+3)+ ( x+4)+.....+( x+9)+ ( x+10) = 2015
Giải:Ta có:\(\left(x+1\right)+\left(x+2\right)+......+\left(x+10\right)=2015\)
\(\Rightarrow x+1+x+2+.....+x+10=2015\)
\(\Rightarrow10x+\left(1+2+......+10\right)=2015\)
\(\Rightarrow10x+55=2015\Rightarrow10x=2015-55\)
\(\Rightarrow10x=1960\Rightarrow x=196\)
Vậy .....................
Câu 1: Tìm x,y,z biết 2x/3=3y/4=4z/5 và x-2y+3z=-31
Câu 2: Tìm x biết x-6/7+x-7/8+x-8/9=x-9/10+x-10/11+x-11/12
Câu 3: Cho A = 1/15+1/16+1/17+....+1/44
CMR: A >5/6
1.tìm M biết :
( m+5)+(m+9)+(m+13)+......+(m+81)=900
2.tìm x biết :
a. (x+2)+(7+x)+9)+(x+12)+...+(x+97)=1990
b.(x+1)+(x+2)+(x+3)+...+(X+9)+(X+10)=65
Bài 1.Tìm x biết
a) ( x - 3 )( x2+ 3x + 9 ) + x( x + 2 )( 2 - x ) = 0.
b) ( x + 1 )3- ( x - 1 )3- 6( x - 1 )2 = - 10.
\(a,\left(x-3\right)\left(x^2+3x+9\right)+x\left(x+2\right)\left(2-x\right)=0\\ \Rightarrow\left(x^3-27\right)+x\left(4-x^2\right)=0\\ \Rightarrow x^3-27+4x-x^3=0\\ \Rightarrow4x-27=0\\ \Rightarrow4x=27\\ \Rightarrow x=\dfrac{27}{4}\)
\(b,\left(x+1\right)^3-\left(x-1\right)^3-6\left(x-1\right)^2=-10\\ \Rightarrow\left(x^3+3x^2+3x+1\right)-\left(x^3-3x^2+3x-1\right)-6\left(x^2-2x+1\right)=-10\\ \Rightarrow x^3+3x^2+3x+1-x^3+3x^2-3x+1-6x^2+12x-6+10=0\)
\(\Rightarrow12x+6=0\\ \Rightarrow12x=-6\\ \Rightarrow x=-\dfrac{1}{2}\)