7.9-14=63-14=49

3-17=-14

Trả lời

7.9-14=63-14=49

3-17=-14

Học tốt nha !

a)\(7.9-14\)

\(=63-14\)

\(=49\)

b)\(3-17=-14\)

_Y nguyệt_

\(\frac{7.9-14}{3-17}=\frac{63-14}{3-17}=\frac{49}{-14}=\frac{-49}{14}\)\(=\frac{-7}{2}\)

\(a,\frac{7.9-14}{3-17}=\frac{63-14}{3-17}=\frac{49}{-14}=\frac{-49}{14}=\frac{-7}{2}\)

TK MÌNH NHE!

CHÚC HỌC TỐT

7 x 9 - 14 / 3 - 17

= ( 7 x 9 ) - ( 14 / 3 ) - 17

= 63 - 14/3 - 17

= 124/3

zzz chúc học giỏi zzz

7 x 9 - 14/3 - 17

= 63 - 14/3 - 17

= 58/1/3 - 17

= 41/1/3

\(\dfrac{5}{12}+\dfrac{3}{16}=\dfrac{5\cdot4+3\cdot3}{48}=\dfrac{29}{48}\)

\(\dfrac{4}{15}-\dfrac{2}{9}=\dfrac{4\cdot3-2\cdot5}{45}=\dfrac{2}{45}\)

a) \(\dfrac{5}{12}+\dfrac{3}{16}=\dfrac{20}{48}+\dfrac{9}{48}=\dfrac{29}{48}\)

b) \(\dfrac{4}{15}-\dfrac{2}{9}=\dfrac{12}{45}-\dfrac{10}{45}=\dfrac{2}{45}\)

\(a,\dfrac{5}{12}+\dfrac{3}{16}=\dfrac{20}{48}+\dfrac{9}{48}=\dfrac{29}{48}\)

\(b,\dfrac{4}{15}-\dfrac{2}{9}=\dfrac{12}{45}-\dfrac{10}{45}=\dfrac{12-10}{45}=\dfrac{2}{45}\)

a) $371+731-271-531$

$=(371-271)+(731-531)$

$=100+200$

$=300$

b) $57+58+59+60+61-17-18-19-20-21$

$=(57-17)+(58-18)+(59-19)+(60-20)+(61-21)$

$=40+40+40+40+40$

$=40\cdot5$

$=200$

c) $9-10+11-12+13-14+15-16$

$=(9-10)+(11-12)+(13-14)+(15-16)$

$=-1+(-1)+(-1)+(-1)$

$=-1\cdot4$

$=-4$

$\text{#}Toru$

\(\dfrac{3}{5}+\dfrac{13}{25}-\dfrac{5}{9}-\dfrac{3}{7}\)

\(=\dfrac{15}{25}+\dfrac{13}{25}-\dfrac{35}{63}-\dfrac{27}{63}\)

\(=\dfrac{28}{25}-\dfrac{62}{63}=\dfrac{214}{1575}\)

bằng 214/1575

Ta có: 

\(\dfrac{2}{5.7}=\dfrac{7-5}{5.7}=\dfrac{1}{5}-\dfrac{1}{7}\)

\(\dfrac{2}{7.9}=\dfrac{9-7}{7.9}=\dfrac{1}{7}-\dfrac{1}{9}\)

..........

\(\dfrac{2}{53.55}=\dfrac{55-53}{53.55}=\dfrac{1}{53}-\dfrac{1}{55}\)

\(\Rightarrow\dfrac{2}{5.7}+\dfrac{2}{7.9}+...+\dfrac{2}{53.55}=\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{5}+...+\dfrac{1}{53}-\dfrac{1}{55}=\dfrac{1}{5}-\dfrac{1}{55}=\dfrac{10}{55}=\dfrac{2}{11}\)

\(=\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{9}+...+\dfrac{1}{53}-\dfrac{1}{55}=\dfrac{1}{5}-\dfrac{1}{55}=\dfrac{2}{11}\)

2/11

\(j,\dfrac{2}{5.7}+\dfrac{2}{7.9}+...+\dfrac{2}{53.55}=\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{9}+...+\dfrac{1}{53}-\dfrac{1}{55}=\dfrac{1}{5}-\dfrac{1}{55}=\dfrac{11}{55}-\dfrac{1}{55}=\dfrac{10}{55}=\dfrac{2}{11}\\ k,\dfrac{1}{2}.\dfrac{2}{3}.\dfrac{3}{4}.\dfrac{4}{5}...\dfrac{99}{100}=\dfrac{1}{100}.\dfrac{2}{2}.\dfrac{3}{3}...\dfrac{99}{99}=\dfrac{1}{100}.1.1...1=\dfrac{1}{100}\)

\(a,\left(2x-5\right)\left(5-x\right)=5\left(2x-5\right)-x\left(2x-5\right)=10x-25-2x^2+5x=15x-2x^2-25\\ b,\dfrac{1}{3x-2}-\dfrac{1}{3x+2}=\dfrac{3x+2-3x+2}{\left(3x-2\right)\left(3x+2\right)}=\dfrac{4}{\left(3x-2\right)\left(3x+2\right)}\)

\(c,\dfrac{3}{x-3}-\dfrac{6x}{x^2-9}+\dfrac{x}{x+3}=\dfrac{3\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}-\dfrac{6x}{\left(x-3\right)\left(x+3\right)}+\dfrac{x\left(x-3\right)}{\left(x-3\right)\left(x+3\right)}=\dfrac{3x+9-6x+x^2-3x}{\left(x-3\right)\left(x+3\right)}=\dfrac{x^2-6x+9}{\left(x-3\right)\left(x+3\right)}=\dfrac{\left(x-3\right)^2}{\left(x-3\right)\left(x+3\right)}=\dfrac{x-3}{x+3}\)