Tính : -245 – (-195) + 150 =
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
295 –[245-(195-245)]
=295-245-195+245
=(295-195)+(245-245)
=100+0=100
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(x+5\right):36=245\)
\(\left(x+5\right)=245\cdot36\)
\(\left(x+5\right)=281\)
\(x=281-5\)
\(x=276\)
Tich nha mk là người trả lời đàu tiên
![](https://rs.olm.vn/images/avt/0.png?1311)
1/3 + 1/15 + 1/35+ 1/63 +...... + 1/195
= 1/3 + 1/3x5 + 1/5 x7 + 1/7x9 + ....+1/13x15
= 1/3+1/3-1/5+1/5-1/7+1/7-1/9+....+1/13-1/15 ( vì +- nên rút gọn )
= 1/3+1/3-1/15
=3/5
=1/1.3+1/3.5+1/5.7+...+1/13.15
=1/2.2(1/1.3+1/3.5+1/5.7+...+1/13.15)
=1/2(2/1.3+2/3.5+2/5.7+...+2/13.15)
=1/2(1-1/3+1/3-1/5+1/5-1/7+...+1/13-1/15)
=1/2[(1-1/15)+(1/3-1/3)+(1/5-1/5)+...+(1/13-1/15)]
=1/2[(1-1/15)+0+...+0=1/2(1-1/15)=1/2.14/15=14/30=7/15
![](https://rs.olm.vn/images/avt/0.png?1311)
1/5.7+1/7.9+1/99.11+...+1/13.15
=1/2(2/5.7+2/7.9+...+2/13.15)
=1/2.(1/2-1/15)
=1/2.13/30
=13/60
ta có :
B = 1 / 5 x 7 + 1 / 7 x 9 + 1 / 9 x 11 + ... + 1 / 13 x 15
2 x B = 2 / 5 x 7 + 2 / 7 x 9 + 2 / 9 x11 + ... + 2 / 13 x 15
2 x B = 1/5 - 1/7 + 1/7 - 1/9 + 1/9 - 1/11 + ... + 1 /13 - 1/15
2 x B = 1/5 - 1/15
2 x B = 3 / 15 - 1/15
2 x B = 2/15
B = 2 / 15 : 2
B = 1/15
vậy B = 1/15
![](https://rs.olm.vn/images/avt/0.png?1311)
\(B=\frac{4}{35}+\frac{4}{63}+\frac{4}{99}+\frac{4}{143}+\frac{4}{195}\)
\(B=2\cdot\left(\frac{2}{5\cdot7}+\frac{2}{7\cdot9}+\frac{2}{9\cdot11}+\frac{2}{11\cdot13}+\frac{2}{13\cdot15}\right)\)
\(B=2\cdot\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}\right)\)
\(B=2\cdot\left(\frac{1}{5}-\frac{1}{15}\right)\)
\(B=2\cdot\frac{2}{15}\)
\(B=\frac{4}{15}\)
B = 4/35 + 4/63 + 4/99 + 4/143 + 4/195
B = 4/5.7 + 4/7.9 + 4/9.11 + 4/11.13 + 4/13.15
B = 4/2 . ( 2/5.7 + 2/7.9 + 2/9.11 + 2/11.13 + 2/13.15 )
B = 4/2 . ( 1/5 - 1/7 + 1/7 - 1/9 + 1/9 - 1/11 + 1/11 - 1/13 + 1/13 - 1/15 )
B = 4/2 . ( 1/5 - 1/15 )
B = 4/2 . 2/15
B = 4/15
![](https://rs.olm.vn/images/avt/0.png?1311)
X x 25 - X x 13 = ( 245 : 5 + 150 ) x 3
X x ( 25 - 13 ) = 597
X x 12 = 597
X = 49,75
Vậy x = 49.75
=-245 + 195 + 150
=-150 + 150
=0
Nha bạn
Đào Ngọc Minh Thư
=-245 + 195 + 150
=-150 + 150
=0
Nha bạn