c) Ta có: \(\dfrac{3}{5}+\dfrac{-5}{20}+\dfrac{30}{75}+\dfrac{-7}{4}\)

\(=\dfrac{3}{5}+\dfrac{2}{5}+\dfrac{-1}{4}+\dfrac{-7}{4}\)

\(=1-2=-1\)

Giải:

a)-1/12+4/3=-1/12+16/12=15/12=5/4

b)(-4/14-3/15)-(1/5-20/35-(-1)).7

=-17/35-22/35.7

=-17/35-22/5

=-171/35

c)3/5+-5/20+30/75+-7/4

=3/5+-1/4+2/5+-7/4

=(3/5+2/5)+(-1/4+-7/4)

=1+-2

=-1

d)5/6.-12/14+7/13

=-5/7+7/13

=-16/91

e)2/-9-5/-36-1/4

=-1/12-1/4

=-1/3

f)2/23+-5/12+7/18+21/23+-7/12

=(2/23+21/23)+(-5/12+-7/12)+7/18

=1+-1+7/18

=7/18

xcsxccsz

=(1 - 2 - 3 + 4) + (5 - 6 - 7 + 8) + ......+ ( 21 - 22 - 23 + 24)

= 0+0+0+......+0

=0 nha

1-2-3+4+5-6-7+8+.....+21-22-23+14

=(1-2-3+4)+(5-6-7+8)+....+(21-22-23+24)

=0+0+...+0

=0

1 - 2 - 3 + 4 + 5 - 6 - 7 + 8 +...+ 21 - 22 - 23 + 24

= (1-2-3+4) + (5-6-7+8) + .... + (21-22-23+24)

= 0 + 0 + ... + 0

= 0

Hok tốt !

1−2−3+4+5−6−7+8+...+21−22−23+24+25

= (1 - 2 - 3 + 4) + (5 - 6 - 7 + 8) + ... + (21 - 22 - 23 + 24) + 25=(1−2−3+4)+(5−6−7+8)+...+(21−22−23+24)+25

= 0 + 0 + ... + 0 + 25=0+0+...+0+25

= 25

\(a,1-2+3-4+5-6+......+199-200\)

\(=\left(1-2\right)+\left(3-4\right)+\left(5-6\right)+.....+\left(199-200\right)\)( 100 cặp )

\(=-1+\left(-1\right)+\left(-1\right)+........+\left(-1\right)\)( 100 số hạng )

\(=-1.100\)

\(=-100\)

\(a.1-2+3-4+5-6+...+199-200\)

\(=\left(1-2\right)+\left(3-4\right)+\left(5-6\right)+...+\left(199-200\right)\)  (có tất cả \(200:2=100\)cặp)

\(=\left(-1\right)+\left(-1\right)+\left(-1\right)+...+\left(-1\right)\)

\(=\left(-1\right).200=-200\)

\(b.1+2-3-4+5+6-7-8+...+97+98-99-100\)

\(=\left(1+2-3-4\right)+\left(5+6-7-8\right)+...+\left(97+98-99-100\right)\)  (có \(100:4=25\)cặp)

\(=\left(-4\right)+\left(-4\right)+...+\left(-4\right)\)

\(=\left(-4\right).25=-100\)

\(c.1+\left(-6\right)+11+\left(-16\right)+...+21+\left(-26\right)\)

\(=\left[1+\left(-6\right)\right]+\left[11+\left(-16\right)\right]+...+\left[21+\left(-26\right)\right]\) (có tất cả \(26:2=13\)cặp)

\(=\left(-5\right)+\left(-5\right)+...+\left(-5\right)\)

\(=-5.13=-65\)

Câu a tớ làm sai, bạn tham khảo của bạn kia nhé!

 \(\left(-\frac{3}{4}+\frac{59}{9}\right):\left(-\frac{7}{23}\right)+\left(\frac{5}{9}-\frac{1}{4}\right):\frac{7}{23}\)

= \(\left(-\frac{3}{4}+\frac{59}{9}\right).\left(-\frac{23}{7}\right)+\left(\frac{5}{9}-\frac{1}{4}\right).\left(\frac{23}{7}\right)\)

=\(\left(-\frac{23}{7}\right).\left(-\frac{3}{4}+\frac{59}{9}-\frac{5}{9}+\frac{1}{4}\right)\)

=\(\left(-\frac{23}{7}\right).\left(-\frac{2}{4}+\frac{54}{9}\right)=\left(-\frac{23}{7}\right).\left(-\frac{1}{4}+6\right)\)

=\(\left(-\frac{23}{7}\right).\frac{11}{2}=-\frac{253}{14}\)

1 - 2 - 3 + 4 + 5 - 6 - 7 + 8 + ... + 21 - 22 - 23 + 24 + 25.

=(1 - 2 - 3 + 4) + (5 - 6 - 7 + 8) + ......+ ( 21 - 22 - 23 + 24)+25

= 0+0+0+......+0+25

=0+25

=25

~HT~

@Jennie

mk nghĩ ko cần giải thik đâu

vì mk ghép các cặp lại để ra kq bằng 0

sau đó cộng thêm 25

là ra kq 25

~HT

#Jennie

k)(-37)+14+26+37

=(-37)+37+14+26

=0+14+26

=40

l)15+23+(-25)+(-23)

=15+(-25)+23+(-23)

=-10+0

=-10

n)25+37-48-25-37

=25-25+37-37-48

=0+0-48

=-48

o)24.(16-5)-16.(24-5)

=24.16-24.5-16.24-16.5

=0-24.5-16.5

=0-(24-16).5

=0-8.5

=0-40

=-40

p)31.(-18)+31.(-81)-31

=31.(-18)+31.(-81)+31.(-1)

=31.[-18+(-81)+(-1)]

=31.(-100)

=-3100

q)-48+48.(-78)+48.(-21)

=48.(-1)+48.(-78)+48.(-21)

=48.[(-1)+(-78)+(-21)]

=48.(-100)

=-4800

r)(7.3-3):(-6)

=(7.3-1.3):(-6)

=(6.3):(-6)

=-3

s)-3.7-4.(-5)+1

=-21-(-20)+1

=-20-(-20)

=0

t(6.8-10:5)+3.(-7)

=(48-2)+(-21)

=46+(-21)

=25

Viết mỏi cả tay rồi.tick đi nhé

\(1\frac{4}{25}+\frac{7}{21}-\frac{4}{25}+0,5+\frac{14}{21}\)

\(=\left(1\frac{4}{25}-\frac{4}{25}\right)+\left(\frac{7}{21}+\frac{14}{21}\right)+0,5\)

\(=1+0+0,5\)

\(=1,5\)

\(15\frac{1}{4}:\frac{-5}{8}-25\frac{1}{4}:\frac{-5}{8}\)

\(=-\frac{8}{5}.\left(15\frac{1}{4}-25\frac{1}{4}\right)\)

\(=-\frac{8}{5}.\left(-10\right)\)

\(=16\)