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a. 8 + (x - 9) = 125 - 64
8 + (x - 9) = 61
x - 9 = 53
x = 62
b. 5 x (X + 7) - 10 = 8 x 5
5 x (X + 7) - 10 = 40
5 x (X + 7) = 50
X + 7 = 10
X = 3
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A=1+2+3+...+70
A=(70+1).[(70-1):1+1]:2
A=71.70:2
A=4970:2
A=2485
B=5+10+15+...+100
B=(100+5).[(100-5):5+1]:2
B=105.20:2
B=2100:2
B=1050
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a, 568 + 568 x 135 - 568 x 36
= 568 x ( 1 + 135 - 36)
= 568 x 100
56 800
b, 17 x 49 + 49 x 37 + 54 x 26 + 54 x 25
= 49 x ( 17 + 37) + 54 x ( 26 + 25 )
= 49 x 54 + 54 x 51
= 54 x ( 49 + 51)
= 54 x 100
= 5 400
c, 14 x 35 x 5 + 10 x 25 x 7 + 20 x 70
= ( 2 x 35) x ( 7 x 5) + ( 10 x 7) x 25 + 20 x 70
= 70 x 35 + 70 x 25 + 20 x 70
= 70 x ( 35 + 25 + 20)
= 70 x 80
= 5 600
a) 568 + 568 x 135 - 568 x 36
= 568 x ( 1+1+135-1-36 )
=568 x 100
=5680
b) 17 x 49 + 49 x 37 + 54 x 26 + 54 x 25
= 49 x ( 17 + 37 ) + 54 x ( 26 + 25 )
= 49 x 54 + 54 x 51
= 54 x ( 49 + 51 )
= 54 x 100
= 5400
c) 14 x 35 x 5 + 10 x 25 x 7 + 20 x 70
= 70 x 35 + 10 x 25 x 7+ 20 x 70
= 70 x 35 + 250 x 7 + 20 x 70
= 70 x 35 + 70 x 25 + 20 x 70
= 70 x (35+25+20)
= 70 x 80
= 5600
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Câu 1 : Tìm số tự nhiên a , biết :
( a + 1 ) + ( a + 2 ) + ( a + 3 ) +...+ ( a + 49 ) + ( a + 50 ) = 2525
(a+a+...+a) +(1+2+3+...+50)=2525
50 SH a
50 . a+(50+1).25=2525
50.a + 1275=2525
50.a=2525-1275
50.a=1250
a=1250:50
=>a=25
TICK ĐI RỒI MIK LÀM TIẾP CHO
So so hang la (50-1):1+1=50(so hang)
(a+a+a+...+a)+(1+2+3+...+50)=2525
(a*50)+(50+1)*50:2=2525
a*50+1275=2525
a*50=2525-1275
a*50=1250
a=1250:50
a=25
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(4900 +490 + 49 x 2) : (700 + 70 +7 x 2) = 7
Nhớ click cho mik nha !!!!!!!!!!!!!!!!!!!!!!!!!
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\(49.5-\left(2x+1\right)=70\)
\(\Leftrightarrow405-2x-1=70\)
\(\Leftrightarrow-2x=70-405+1\)
\(\Leftrightarrow-2x=-344\)
\(\Leftrightarrow x=172\)
~ học tốt !~
49 . 5 - ( 2x + 1 ) = 70
<=> 405 - 2x - 1 = 70
<=> -2 = 70 - 405 + 1
<=> -2x = -344
<=> x= 172