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bạn phá ngoặc ra và nhớ là nếu trước dấu () là - thì đổi dấu bên trong ngoặc, còn + thì giữ nguyên đầu trong ()
VD: a. (8576-535)-8576= 8576-535-8576=-535
a) (8576 - 535) - 8576
= (8676 - 8576) - 535
= 0 - 535
= -535
b) (-7165) - (155 - 7165)
= -7165 - 155 + 7165
= (-7165 + 7165) - 155
= 0 - 155
= -155
c) -8715 + (1345 + 8715)
= -8715 + 1345 + 8715
= (-8715 + 8715) + 1345
= 0 + 1345
= 1345
d) (35 - 815) - (795 - 65)
= 35 - 815 - 795 + 65
= (35 + 65) - 815 - 795
= 100 - 1610
= -1510.
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Bài 5 :\(a,\left(8576-535\right)-8576\)
\(=8576-535-8576\)
\(=\left(8576-8576\right)-535\)
\(=0-535\)
\(=-535\)
\(b,\left(-7105\right)-\left(155-7105\right)\)
\(=-7105-155+7105\)
\(=\left(-7105+7105\right)-155\)
\(=0-155\)
\(=-155\)
\(c,8715+\left(1345+8715\right)\)
\(=8715+1345+8715\)
\(=8715\times2+1345\)
\(=17430+1345\)
\(=18775\)
\(d,\left(35-815\right)-\left(795-65\right)\)
\(=35-815-795+65\)
\(=\left(35+65\right)-\left(815+795\right)\)
\(=100-1610\)
\(=-1510\)
Bài 6 : \(a,25-\left(30+x\right)=x-\left(27-8\right)\)
\(25-30-x=x-19\)
\(-x-x=-19-25+30\)
\(-2x=-14\)
\(x=7\)
\(b,\left(x-2\right)-15=\left(20-7\right)-\left(18+x\right)\)
\(x-2-15=13-18-x\)
\(x+x=13-18+2+15\)
\(2x=12\)
\(x=6\)
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1. a, (8576 + (-536)) - 8576
= 8576 - 536 - 8576
= -536
b, (-7105) - (155 - 7105)
= -7105 - 155 + 7105
= -155
c,-8715+ (1345 + 8715)
= -8715 + 1345 + 8715
= 1345
d,(35 - 815) - (795 - 65)
= 35 - 815 - 795 + 65
= ( 35 + 65 ) + (-815 - 795)
= 100 - 1610
= -1510
e,f, bạn làm tương tự nhé!
Bài 2:a, / a - 2/ = 0
a - 2 = 0
a = 2
b, bạn ghi sai đề rồi
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Tính nhanh :
394.768+606.769+394 = 394(768+1) +606.769 = 394.769 + 606.769 = 769(394+606) = 769.1000 = 769 000
B=232323.79 - 797979.23 = 10101.23.79 - 10101.79.23 = 0
Tính hợp lí : 22344.36+44688.82 = 22344.2.18 + 44688.82 = 44688 . (18+82 ) = 44688.100 = 4 468 800
394.768+606.769+394
= 394 (768+1)+606.769
= 394.769+606.769
= 769 (394+606)
= 769.1000 = 769000
232323.79-797979.23
= (10101.23).79-(10101.79).23
= 10101.23.79-10101.79.23
= 0
22344.36+44688.82
= 22344.36.2:2+44688.82
= (22344.2).(36:2)+44688.82
= 44688.18+44688.82
= 44688 (18+82)
= 44688.100 = 4468800
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\(\frac{-7}{21} +\left(1+\frac{1}{3}\right)\)
\(=\frac{-1}{3}+1+\frac{1}{3}=1\)
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a) 11x2x11x9
b)11x3x11x3
c)111x3x111x3
d)1111x3x1111x3
mình tách ra cho b vế đầu phần tính nhanh r b làm tiếp nhé
#chanh
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Tính nhanh:
a) 135 + 360 + 64 + 40;
= ( 65 + 135) + ( 360 + 40)
= 200 + 400
= 600
b) 463 + 318 + 137 + 22;
= ( 463 + 137) + ( 318 + 22)
= 600 + 314
= 914
c) 20 + 21+ 22 + ... + 29 + 30.
= ( 20 + 30 ) + ( 21 + 29 ) + ( 22 + 28) + ( 23 + 27) + ( 24 + 26) + 25.
= 5. 50 + 25
= 250 + 25
= 275
a) 135 + 360 + 65 + 40 = (135 + 65) + (360 + 40) = 200 + 400 = 600.
b) 463 + 318 + 137 + 22 = (463 + 137) + (318 + 22) = 600 + 340 =940.
c) Nhận thấy 20 + 30 = 50 = 21 + 29 = 22+ 28 = 23 + 27 = 24 + 26.
Do đó 20 + 21 + 22 + ...+ 29 + 30
= (20+ 30) + (21 + 29) + (22 + 28) + (23 + 27) + (24 + 26) + 25
= 5 . 50 + 25 = 275.
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41.36+59.90+41.81+59.30=11877
4.51.7+2.86.7+12.2.7=2800
x=1964
x=1500
(8576-535)-8576
=8576-8576-535
=0-535
=-535
( 8576 - 535 ) - 8576
= 8576 - 8576 - 535
= 0 - 535 = -535