15 - 2x = 11
=> 2x = 15 - 11
=> 2x = 4
=> x = 4 : 2 = 2
3.(x - 9) + 15 = 81
=> 3x - 27 = 81 - 15
=> 3x - 27 = 66
=> 3x = 66 + 27
=> 3x = 93
=> x = 93 : 3 = 31
a) 15 - 2.x = 11
2.x = 4
x = 2
b) 3. (x - 9) + 15 = 81
3. (x - 9) = 66
x - 9 = 22
x = 31
c) (x+1)+(x+2)+...+(x+10)= 105
(x+x+....+x) + (1+2+....+10) = 105
x . 10 + 55 = 105
x . 10 = 50
x = 5
a, 15 - 2x = 11
=> 2x = 4
=> x = 2
vay_
b, 3(x - 9) + 15 = 81
=> 3(x - 9) = 66
=> x - 9 = 22
=> x = 31
vay_
c, (x + 1) + (x + 2) + (x + 3) + ... + (x + 10) = 105
=> x + 1 + x + 2 + x + 3 + ... + x + 10 = 105
=> (x + x + x + ... + x) + (1 + 2 + 3 + ... + 10) = 105
=> 10x + 55 = 105
=> 10x = 50
=> x = 5
vay_
(x + 1) + (x + 2) + (x + 3) + ... + (x + 10) = 105
=> (x + x + x + ... + x) + (1 + 2 + 3 + ... + 10) = 105
=> 10x + 55 = 105
=> 10x = 105 - 55
=> 10x = 50
=> x = 5
a,15-2.x=11
2.x=15-11
2.x=4
x=4
b,3.(x-9) +15=81
3.(x-9)=81-15=66
x-9=66:3
x-9=22
x=13
c,(x+1)+(x+2)+....+(x+10)=105
(x+x+...+x)+(1+2+3+...+10)
X.10+55=105
x.10=105-55
x.10=50
x=5
1)
a) 15-2x=11
2x=15-11
2x=4
x=4:2
x=2. Vậy x=2.
b) 3(x-9)+15=81
3(x-9)=81-15
3(x-9)=66
x-9=66:3
x-9=22
x=22+9
x=31. Vậy x=31.
c) (x+1)+(x+2)+...+(x+10)=105
=> (x+x+x+...+x)+(1+2+...+10)=105
10 số x
Đặt A là 1+2+3+...+10
=> A= (10+1).10:2=55
=> 10x+55=105
=>10x=105-55
=>10x=50
=> x=50:10
=> x=5. Vậy x=5.
_Học tốt_
\(1,\)
\(a,\)\(15-2.x=11\)
\(2.x=15-11\)
\(2.x=4\)
\(x=4:2\)
\(x=2\)
\(b,\)\(3.\left(x-9\right)+15=81\)
\(3.\left(x-9\right)=81-15\)
\(3.\left(x-9\right)=66\)
\(x-9=66:3\)
\(x-9=22\)
\(x=22-9\)
\(x=13\)
\(c,\)\(\left(x+1\right)+\left(x+2\right)+\left(x+3\right)+...+\left(x+10\right)=105\)
\(x+\left(1+2+3+...+10\right)=105\)
\(x+55=105\)
\(x=105-55\)
\(x=50\)
\(Xong\)\(r\)\(bn\)\(!!!\)
a) 15 - 2x = 11
=> 2x = 4
=> x = 2
b) 3. ( x - 9 ) + 15 = 81
=> 3. ( x - 9 ) = 66
=> x - 9 = 22
=> x = 31
c) (x + 1) + (x + 2) + (x + 3) .........(x + 10) = 105
=>( x + x + ....+ x ) + ( 1 + 2 + 3 + 4 + .... + 10 ) = 105
=> x . 10 + 55 = 105
=> x . 10 = 50
=> x = 5