A = 1 + ( -3 ) + 5 + ( - 7 ) + ... + 17 + ( - 19 )
Dẫy A có số số hạng là : ( 19 - 1 ) : 2 + 1 = 10 ( số )
Có số số cặp là : 10 : 2 = 5 ( cặp )
Ta có :
A = [ 1 + ( -3 ) ] + [ 5 + ( - 7 ) ] + ... + [ 17 + ( - 19 ) ] ( 5 cặp )
A = ( - 2 ) + ( - 2 ) + ... + ( - 2 ) ( 5 số hạng -2 )
A = ( - 2 ) . 5
A = - 10
Complete the sentences.
16. This box is too heavy for Tom and me. Could you help ___________to lift it, please?
17. What beautiful roses! Who gave ______________to you?
18. My soup is tasteless. Can you pass ______________the salt, please?
19. Have you seen my keys? I can't find ______________anywhere.
20. There is a new girl in your class, do you know ______________?
a)17×81+19×17-150
b)20-[50-(5-1)^2]
c)44+7×x=10^3:10
d)/x-1/+3=5
Tìm số a chia hết cho 9
Help me😦😦😳
1. Tính (bằng cách hợp lý nhất0
a, -2/5. 4/7 + -3/5 . 2/7 + -3/5
b,5/9.14/17+1/17.5/9+ 2/9 . 5/12
c,-4/25: 11/79 +15/11:25/79
d, (2/101: -5/9 + -3/7). (6/5-2/5:1/3)
Please help me!!!
1) A = 1/1.3 + 1/2.4 + 1/3.5 + ... + 1/7.9 + 1/8.10
2) Chứng minh:
3/1^2.2^2 + 5/2^2.3^2 + 5/3^2.4^2 + ... + 19/9^2.10^2 < 1
Help me, please!!!!!!!!!!!
Bạn nào biết đề khảo sát chất lượng đầu năm lớp 7 thì cho mình nha!
A= -3/3 - 7/17 + -5/19 + 10/13 + 24/27 - 14/19
B= 1,25 * 7/19 + 5/4 * 15/19 - 1* 1/4 / 19/3
a,-8/3+7/5+-71/15<x<-13/7+19/14+-7/2
b,-19/6+-15/2+11/3<x<-5/4+19/12+-10/3
c,-6/7+3/35<x<-2/5+3/7
d,x=3/4+1/-12
e,x/14=1/7+-3/14
f,11/18+13/6=85/x
g,8/17+5/17<x/17<6/17+9/17
-1/3*141/17-39/3*-1/17
7/13*5/19+7/19-8/13
bài 1
a. 5/18 + 8/19 - 7/21 + ( -10/36 + 11/19 + 1/3) - 5/8
b.1/13 + ( -5/18 - 1/13 + 12/17 ) - ( 12/17 - 5/18 + 7/5 )
c.15/14 - (17/23 - 80/87 + 5/4)+(17/23 - 15/14 + 1/4 )
d.1/25 - 4/27 + ( -23/27 + -1/25 - 5/43 ) + 5/43 - 4/7
bài 2
a. x +1/3 = 3/4
b. x - 2/5 = 5/7
c. -x - 2/3 = -6/7
d. 4/7 - x = 1/3
e. x+ 5/2 = -3/2
f. x + 5/6 = -1/12
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