a.5/14+1/2=6/7

b.5/3-1=2/3

c.4/3-1/3=1

a) 5/14+ 1/2= 6/7

b) 5/3 - 1= 2/3

c) 4/3- 1/3 =1

a.5/14+1/2=6/7

b.5/3-1=2/3

c.4/3-1/3=1

`1`

`a, 1/2 +1/3= 3/6 + 2/6 =5/6`

`d, 1/3 +3/5= 5/15 + 9/15=14/15`

`c,4/5 +1/2= 8/10 + 5/10= 13/10`

`2`

`a,1/2 +1/4=2/4 +1/4=3/4`

`b, 2/3 +1/6 = 4/6+1/6=5/6`

`c, 7/12 +1/2=7/12+ 6/12= 13/12`

`3`

Giải

Cả `2` ngày đi tất cả số quãng đường là :

`1/4 +1/2 =1/4+ 2/4= 3/4 ( quãng đường)`

đ/s...

`@ yL`

a, \(1+\dfrac{3}{4}=\dfrac{7}{4}\)

b, \(\dfrac{4}{5}-\dfrac{3}{8}=\dfrac{32-15}{40}=\dfrac{17}{40}\)

c, \(1:\dfrac{2}{3}=\dfrac{1.3}{2}=\dfrac{3}{2}\)

d, \(\dfrac{2}{5}.\dfrac{5}{2}=1\)

a)1 + 3/4=7/4

   b)4/5 -3/8=17/40

  c)1 : 2/3=3/2

  d)2/5 x 5/2=1

Đáp án:

a)1 + 3/4=7/4

b)4/5 -3/8=17/40

c)1 : 2/3=3/2

d)2/5 x 5/2=1

\(a,\dfrac{1}{2-\sqrt{3}}-3\sqrt{\dfrac{1}{3}}+\sqrt{12}\\ =\dfrac{2+\sqrt{3}}{\left(2-\sqrt{3}\right)\left(2+\sqrt{3}\right)}-\dfrac{\sqrt{3^2}}{\sqrt{3}}+\sqrt{2^2.3}\\ =\dfrac{2+\sqrt{3}}{4-3}-\sqrt{3}+2\sqrt{3}\\ =2+\sqrt{3}-\sqrt{3}+2\sqrt{3}\\ =2+2\sqrt{3}\)

\(b,\dfrac{2}{1+\sqrt{2}}-\sqrt{9-\sqrt{32}}\\ =\dfrac{2\left(1-\sqrt{2}\right)}{\left(1+\sqrt{2}\right)\left(1-\sqrt{2}\right)}-\sqrt{9-4\sqrt{2}}\\ =\dfrac{2-2\sqrt{2}}{1-2}-\sqrt{\left(2\sqrt{2}\right)^2-2.2\sqrt{2}+1}\\ =-2+2\sqrt{2}-\sqrt{\left(2\sqrt{2}-1\right)^2}\\ =-2+2\sqrt{2}-\left|2\sqrt{2}-1\right|\\ =-2+2\sqrt{2}-2\sqrt{2}+1\\ =-1\)

\(a,\dfrac{1}{3}-\left(-1\dfrac{2}{5}\right)+\left(-3\dfrac{1}{4}\right)\\ =\dfrac{1}{3}-\left(-\dfrac{7}{5}\right)-\dfrac{13}{4}\\ =\dfrac{1}{3}+\dfrac{7}{5}-\dfrac{13}{4}\\ =\dfrac{20}{3\times20}+\dfrac{7\times12}{5\times12}-\dfrac{13\times15}{4\times15}\\ =\dfrac{20+84-195}{60}\\ =\dfrac{-91}{60}\)

\(b,\dfrac{5}{4}-\left(-3\dfrac{1}{2}\right)-\dfrac{7}{10}\\ =\dfrac{5}{4}+\dfrac{7}{2}-\dfrac{7}{10}\\ =\dfrac{5\times5}{4\times5}+\dfrac{7\times10}{2\times10}-\dfrac{7\times2}{10\times2}\\ =\dfrac{25+70-14}{20}\\ =\dfrac{81}{20}\)

\(c,\dfrac{3}{2}-\left[\left(-\dfrac{4}{7}-\left(\dfrac{1}{2}+\dfrac{5}{8}\right)\right)\right]\\ =\dfrac{3}{2}-\left[-\dfrac{4}{7}-\left(\dfrac{4}{8}+\dfrac{5}{8}\right)\right]\\ =\dfrac{3}{2}-\left(-\dfrac{4}{7}-\dfrac{9}{8}\right)\\ =\dfrac{3}{2}+\dfrac{4}{7}+\dfrac{9}{8}\\ =\dfrac{3\times28}{2\times28}+\dfrac{4\times8}{8\times7}+\dfrac{9\times7}{8\times7}\\ =\dfrac{84+32+63}{56}\\ =\dfrac{179}{56}\)

`@` `\text {Ans}`

`\downarrow`

`a,`

\(\dfrac{1}{3}-\left(-1\dfrac{2}{5}\right)+\left(-3\dfrac{1}{4}\right)\)

`= 1/3+7/5 - 13/4`

`= 26/15 - 13/4`

`= -91/60`

`b,`

\(\dfrac{5}{4}-\left(-3\dfrac{1}{2}\right)-\dfrac{7}{10}\)

`= 5/4+7/2 - 7/10`

`= 1,25 + 3,5 - 0,7`

`= 4,75 - 0,7`

`= 4,05`

`c,`

\(\dfrac{3}{2}-\left[\left(-\dfrac{4}{7}\right)-\left(\dfrac{1}{2}+\dfrac{5}{8}\right)\right]\)

`= 3/2 - [(-4/7) - 9/8]`

`= 3/2 - (-95/56)`

`= 179/56`

8507cm2

32m^2 217dm^2=320217

3/5 giờ 12 phút = 48 phút

\(\dfrac{3}{7}.\left(\dfrac{5-1}{4}\right)=\dfrac{3}{7}.1=\dfrac{3}{7}\)

\(\dfrac{11}{10}-\dfrac{6}{10}=\dfrac{5}{10}=\dfrac{1}{2}\)

a)

= 15/28 - 1/4

= 2/7

b)

= 7/10 : 2/3

= 21/20

85m2 7cm2= 850007    cm2

32m217dm2=  3217  dm2

3/5 giờ 12=  48 phút

Tính

a.3/7x5/4-1/4

= 15/28 - 1/4

- 2/7 

b.11/10-2/5:2/3

= 11/10 - 3/5

= 1/2

a: \(=\dfrac{x+1+3}{x-3}=\dfrac{x+4}{x-3}\)

\(a,=4x^2-4x+1-4x^2+4-x^2-x+6=-x^2-5x+11\\ b,=8x^3+27-8x^3+72x=72x+27\)

a) \(=4x^2-4x+1-4\left(x^2-1\right)-\left(x^2-2x+3x-6\right)=4x^2-4x+1-4x^2+4-x^2-x+6=-x^2-5x+11\)

b) \(=8x^3+27-8x\left(x^2-9\right)=8x^3+27-8x^3+72x=72x+27\)

a) `1/9-0,3. 5/9+1/3`

`=1/9-3/10 . 5/9+1/3`

`=1/9-15/90+1/3`

`=1/9-1/6+1/3`

`=2/18-3/18+6/18`

`=5/18`

b) `(-2/3)^2+1/6-(-0,5)^3`

`=4/9+1/6-(-0,125)`

`=4/9+1/6+0,125`

`=4/9+1/6+1/8`

`=32/72+12/72+9/72`

`=53/72`

c: \(=4x^2-12x+9-4x^2+x=-11x+9\)

\(a,=2x^2-10x+x^2+x-6=3x^2-9x-6\\ b,=x^2+4x+4-x^2+8x-15=12x-11\\ c,=4x^2-12x+9-4x^2+x=-11x+9\)