a) \(\left(x-15\right)-35=58\)

\(x-15=58+35\)

\(x-15=93\)

\(x=93+15\)

\(x=108\)

b) \(x-7100=1100+1\)

\(x-7100=1101\)

\(x=1101+7100\)

\(x=8201\)

help mik zới mn ưi

\(\frac{5}{6\cdot7}+\frac{5}{7\cdot8}+\frac{5}{8\cdot9}+...+\frac{5}{100\cdot101}\)   

\(=5\left(\frac{1}{6\cdot7}+\frac{1}{7\cdot8}+\frac{1}{8\cdot9}+...+\frac{1}{100\cdot101}\right)\)   

\(=5\left(\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+...+\frac{1}{100}-\frac{1}{101}\right)\)   

\(=5\left(\frac{1}{6}-\frac{1}{101}\right)\)   

\(=5\left(\frac{95}{606}\right)\)   

\(=\frac{475}{606}\)

Tính

\(\frac{5}{6\times7}+\frac{5}{7\times8}+\frac{5}{8\times10}+...+\frac{5}{100\times101}\)

\(=5\times\left(\frac{1}{6\times7}+\frac{1}{7\times8}+\frac{1}{8\times9}+...+\frac{1}{100\times101}\right)\)

\(=5\times\left(\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+...+\frac{1}{100}-\frac{1}{101}\right)\)

\(=5\times\left(\frac{1}{6}-\frac{1}{101}\right)\)

\(=5\times\frac{95}{606}=\frac{475}{606}\)

\(\text{-12(x-5)+7(3-x)=5 }\)

\(-12x+60+21-7x=5\)

\(-12x-7x=5-21-60\)

\(-19x=-76\)

\(x=-76:\left(-19\right)\)

\(x=4\)

\(\text{ 30(x+2)-6(x-5)-24x=100}\)

\(30x+60-6x+30-24x=100\)

\(30x-6x-24x=100-30-60\)

\(0=10\)

\(\Rightarrow x\)ko tồn tại

\(\text{(x+1-5)+7(3-x)=5 }\)

\(x+1-5+21-7x=5\)

\(x-7x=5-21+5-1\)

\(-6x=-12\)

\(x=\left(-12\right):\left(-6\right)\)

\(x=2\)

\(\text{(x+1)+(x+3)+(x+5)+........+(x+99)=0}\)

\(\text{(x+1)+(x+3)+...+(x+99)=0}\)
tổng các số hang là\(\frac{\left(99+1\right)}{2}=50\)(số hạng)
=>\(\text{(x+1)+(x+3)+...+(x+99)=0}\)<=> \(\text{50.x+(1+3+5+..+99)=0}\)
<=>\(\text{50.x+(99+1)}\)\(.\frac{50}{2}=0\)<=> \(\text{50.x+2500=0=}\)>\(x=\frac{-2500}{50}=-50\)

chúc bạn học tốt

a) \(-12\left(x-5\right)+7\left(3-x\right)=5\)

\(-12x+60+21-7x=5\)

\(-19x=5-60-21\)

\(-19x=-76\)

\(x=4\)

vậy \(x=4\)

tương tự 

1: =-2/9(15/17+2/17)=-2/9

2: \(=\dfrac{-6}{3}+\dfrac{-21}{90}\)

=-2-7/30=-67/30

3: \(=\dfrac{3}{4}\cdot\dfrac{7}{5}+\dfrac{9}{7}\cdot\dfrac{3}{2}\)

=21/20+27/14=417/140

4: =-25/13(5/19+14/19)=-25/13

5: =-7/5-45/21=-7/5-15/7=-124/35

1: =-2/9(15/17+2/17)=-2/9

2: =34⋅75+97⋅32=34⋅75+97⋅32

=21/20+27/14=417/140

4: =-25/13(5/19+14/19)=-25/13

5: =-7/5-45/21=-7/5-15/7=-124/35

9: =3/2*5/12+3/16

=15/24+3/16

=5/8+3/16

=13/16

Giải:

a) \(-12\left(x-5\right)+7\left(3-x\right)=5\) 

       \(-12x+60+21-7x=5\) 

                       \(-12x-7x=5-60-21\) 

                               \(-19x=-76\) 

                                     \(x=-76:-19\) 

                                     \(x=4\) 

b) \(30\left(x+2\right)-6\left(x-5\right)-24x=100\) 

       \(30x+60-6x+30-24x=100\) 

                       \(30x-6x-24x=100-60-30\) 

                                            \(0x=10\) 

Vì ko có số nào mà nhân với 0 mà đc kết quả lớn hơn 0 hay bé hơn 0 mà khi nhân với 0 ta đc kết quả 0 nên \(x\in\) ∅

1. A

2. B

3. A

4. B

1.    444 x 5 = 222 x 2 x 5 = 222 x 10 = 2220
2.    282 x 5 = 280 + 2 x 5 = 280 x 10 = 2800
3.    4 x 8 x 7 x 25 = (8 x 7) x (25 x4) = 56 x 100 = 5600
4.    25 x 8 x 9 = (25 x 4) x (4 x 9) = 100 x 36 = 3600
a.Đúng         b.Sai

1. sai

2. Sai

3. đúng

4.sai

\(-12\cdot\left(x-5\right)+7\cdot\left(3-x\right)=5\)

\(-12\left(x-5\right)+7\left(-x+3\right)=5\)

\(-\left(12x-12\cdot5\right)+\left(-7x+7\cdot3\right)=5\)

\(-\left(12x-60\right)+\left(-7x+21\right)=5\)

\(-12+60+-7x+21=5\)

\(-12x-7x+0+21=5\)

\(-19+81=5\)

\(\left(-19x+81\right)+\left(-81\right)=5+\left(-81\right)\)

\(-19x+81-81=5-81\)

\(-19x=76\)

\(\frac{19x}{19}=\frac{76}{19}\)

\(x=\frac{2^2\cdot19}{19}\)

\(x=2^2=4\)