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a, \(\dfrac{254\times399-145}{254+399\times253}\)
= \(\dfrac{\left(253+1\right)\times399-`45}{254+399\times253}\)
= \(\dfrac{253\times399+399-145}{253\times399+254}\)
= \(\dfrac{253\times399+254}{253\times399+254}\)
= 1
b, \(\dfrac{5932+6001\times5931}{5932\times6001-69}\)
= \(\dfrac{5932+6001\times5931}{\left(5931+1\right)\times6001-69}\)
= \(\dfrac{5932+6001\times5931}{5931\times6001+6001-69}\)
= \(\dfrac{5932+6001\times5931}{5931\times6001+5932}\)
= 1
A)\(\frac{254\cdot399-145}{254+399\cdot253}\)
\(=\frac{\left(253+1\right)\cdot399-145}{254+399\cdot253}\)
\(=\frac{253\cdot399+1\cdot399-145}{254+399\cdot253}\)
\(=\frac{253\cdot399+399-145}{254+399\cdot253}\)
\(=\frac{253\cdot399+254}{254+399\cdot253}\Rightarrow=1\)
B) X x X - 1/6 = 5/18
x2 = 5/18 + 1/6
x2 = 8/18 = 4/9
x= \(\sqrt{\frac{4}{9}}\) \(=\frac{2}{3}\)
a: \(=\dfrac{4\cdot11\cdot3}{4\cdot9}\cdot\dfrac{1}{121}=\dfrac{11}{121}\cdot\dfrac{1}{3}=\dfrac{1}{33}\)
b: \(=\dfrac{7}{9}\left(\dfrac{3}{4}+\dfrac{1}{4}\right)=\dfrac{7}{9}\)
c: \(=\dfrac{-6}{7}-\dfrac{1}{7}+\dfrac{2}{11}+\dfrac{9}{11}+\dfrac{12}{17}=\dfrac{12}{17}\)
\(\frac{254.399-145}{254+399.253}=\frac{253.399+399-145}{253.399+254}=\frac{253.399+254}{253.399+254}=1\)
2: \(=\dfrac{59}{10}\cdot\dfrac{2}{3}-\left[\dfrac{7}{3}\cdot\left(4+\dfrac{1}{2}-2\right)\right]\cdot\dfrac{4}{7}\)
\(=\dfrac{59}{15}-\dfrac{4}{3}\cdot\dfrac{5}{2}=\dfrac{59}{15}-\dfrac{10}{3}=\dfrac{59-50}{15}=\dfrac{9}{15}=\dfrac{3}{5}\)
4: \(=254+254\cdot399+399\)
\(=254\cdot400+399\)
\(=101600+399=101999\)
5: \(=638+3900-41=3900+597=4497\)
a . 254 x 399 - 145 / 254 + 399 x 253 = ( 253 + 1 ) x 399 - 145 / 254 + 399 x 253
= 253 x 399 + 1 x 399 - 145 / 254 + 399 x 253
=253 x 399 + 399 - 145 / 254 + 399 x 253
= 253 x 399 + ( 399 - 145) / 254 + 399 x 253
= 253 x 399 + 254 / 254 + 399 x 253
= 1
b. 1997 x 1996 - 995 / 1995 x 1997 + 1002 = 1997 x ( 1995 + 1 ) - 995 / 1995 x 1997 + 1002
= 1997 x 1995 + 1997 - 1995 / 1995 x 1997 + 1002
= 1997 x 1995 + ( 1997 - 995 ) / 1995 x1997 + 1002
= 1997 x1995 + 1002 / 1995 x 1997 + 1002
= 1
c. 5932 + 6001 x 5031 / 5932 x 6001 - 69 = 5932 + 6001 x 5031 / ( 5031 + 1 ) x 6001 - 69
= 5932 + 6001 x 5031 / 5031 x 6001 + 6001 - 69
= 5932 + 6001 x 5031 / 5031 x 6001 + ( 6001 - 69 )
= 5932 + 6001 x 5031 / 5031 x 6001 + 5932
= 1
d. 1995 x 1997 - 1 / 1996 x 1995 + 1994 = 1995 x ( 1996 + 1 ) - 1 / 1996 x 1995 + 1994
= 1995 x1996 + 1995 - 1 / 1996 x 1995 + 1994
= 1995 x 1996 + ( 1995 - 1 ) / 1996 x 1995 + 1994
= 1995 x 1996 + 1994 / 1996 x 1995 + 1994
= 1
a) A = 1 + 2 + 3 + 4+... + 50;
Tổng A có 50 số hạng nên A = (1 + 50).50:2 = 1275,
b) B = 2 + 4 + 6 + 8 + ...+100;
Số số hạng của tổng B là: (100 - 2): 2+1 = 50 (số)
Do đó B = (2 +100).50 : 2 = 2550.
c) C = 1 + 3 + 5 + 7 +... + 99;
Số số hạng của tổng C là: (99 - 1): 2 +1 = 50 (số)
Do đó C = (1 + 99). 50 : 2 = 2500.
d = 2 + 5 + 8 + 11 .... 98
= ( 92 - 2 ) : 3 + 1 = 33
= 33 . ( 98 + 2 ) : 2
= 1650
tick cho tớ với
a)(689 + 875 ) +125
=1564 + 125
=2944
b)2/7 +4/9 +5/7 + 5/9
=46/63 +80/63
=2
c)581 +878 +419
=(581 +419) +878
=1000+878
=1878
d)254 x 399 -145 /254 + 399 x 253
=399 x (254 +253 ) -145 /254
=399 x 507 -145 /254
=202292,4291
mik nha
them mot cau nua nay
e]5932+6001x5931/5932x6001-69