Câu 9

a) 2/15 + (-3/5)

= 2/15 - 3/5

= 2/15 - 9/15

= -7/15

b) -5/7 + 3/7 . (-2/9)

= -5/7 - 2/21

= -15/21 - 2/21

= -17/21

c) 5/16 - (7/15 - 3/16) + 17/30

= 5/16 - 7/15 + 3/16 + 17/30

= (5/16 + 3/16) + (17/30 - 14/30)

= 1/2 + 1/10

= 5/10 + 1/10

= 6/10

= 3/5

\(a,\dfrac{2}{15}+\left(-\dfrac{3}{5}\right)\\ =\dfrac{2}{15}-\dfrac{3}{5}\\ =\dfrac{2}{15}-\dfrac{9}{15}\\ =-\dfrac{7}{15}\\ b,-\dfrac{5}{7}+\dfrac{3}{7}\times\left(-\dfrac{2}{9}\right)\\ =-\dfrac{5}{7}-\dfrac{2}{21}\\ =-\dfrac{15}{21}-\dfrac{2}{21}\\ =-\dfrac{17}{21}\\ c,\dfrac{5}{16}-\left(\dfrac{7}{15}-\dfrac{3}{16}\right)+\dfrac{17}{30}\\ =\dfrac{5}{16}-\dfrac{7}{15}+\dfrac{3}{16}+\dfrac{17}{30}\\ =\left(\dfrac{5}{16}+\dfrac{3}{16}\right)-\left(\dfrac{17}{15}+\dfrac{17}{30}\right)\\ =\dfrac{1}{2}-\dfrac{17}{10}\\ =\dfrac{5}{10}-\dfrac{17}{10}\\ =-\dfrac{6}{5}.\)

(2/3.5/7 + 2/3: 7/2). -1/3

=(10/21 + 2/3x2/7 ) . -1/3

=(10/21 + 4/21) . -1/3

=-10/63 - 4/63

=-14/63

(2/3.5/7+2/3:7/2)-1/3

=(2/3.5/7+2/3x2/7)-1/3

=[2/3.(5/7+2/7)]-1/3

=[2/3x1]-1/3

=2/3-1/3

=1/3

HT

=[\(\left(\frac{2}{3}.\frac{5}{7}+\frac{2}{3}.\frac{2}{7}\right).\left(\frac{-1}{3}\right)\)]

=[\(\left(\frac{2}{3}\right).\left(\frac{5}{7}+\frac{2}{7}\right).\left(\frac{-1}{3}\right)\)]

=[\(\left(\frac{2}{3}.1\right).\frac{-1}{3}\)]

=\(\frac{-1}{3}\)

Lời giải:

$=3.17+(3.120-3.17)=3.17+3.120-3.17$

$=(3.17-3.17)+3.120=3.120=360$

-3.(-17)+3.(120-17)

= 3.17 + 3.120 - 3.17

= (3.17-3.17) + 3.120

= 0 + 360 = 360

Lời giải:

$-3(-17)+3(120-17)=3.17+3.120-3.17=3.120=360$

xx - 1x × 2 = 34

11 × x - 10 × 2 - x × 2 = 34

(11 - 2) × x - 20 = 34

9 × x = 34 + 20

9 × x = 54

x = 54 : 9

x = 6

\(34\times76+66\times110+34\times34\)

\(=34\times\left(76+34\right)+66\times110\)

\(=34\times110+66\times110=110\times\left(34+66\right)=110\times100=110000\)

34 x 76 + 66 x 110 + 34 x 34

= 34 x ( 76 + 34 ) + 66 x 110

= 34 x 110 + 66 x 110

= 110 x ( 34 + 66 )

= 110 x 100

= 11 000

=))

\(-23\cdot63+23\cdot21-58\cdot23\)

\(=23\left(-63+21-58\right)\)

\(=23\cdot\left(-100\right)\)

\(=-2300\)

Trả lời:

-23 . 63 + 23 . 21 - 58 . 23

= 23 . (-63 + 21 - 58)

= 23 . (-100)

= -2300

Hok tốt!

Vuong Dong Yet

a, 5\(\dfrac{4}{27}\) + \(\dfrac{6}{23}\) + 0,25 - \(\dfrac{4}{27}\) + \(\dfrac{17}{23}\)

= 5 +  (\(\dfrac{4}{27}\) - \(\dfrac{4}{27}\)) + (\(\dfrac{6}{23}\) + \(\dfrac{17}{23}\)) + 0,25

= 5 + 1 + 0,25

= 6,25

b, 16.(\(\dfrac{1}{2}\))³ - \(\dfrac{3}{5}\): 0,75

= 16.\(\dfrac{1}{8}\) - 0,8

= 2 - 0,8

= 1,2

\(B=\left(-25\right)\times68+\left(-34\right)\cdot\left(-250\right)\)

\(\Rightarrow B=-25\times68-34\times\left(-25\right)\times10\)

\(\Rightarrow B=\left(-25\right)\times\left(68-340\right)\)

\(\Rightarrow B=\left(-25\right)\times\left(-272\right)\)

\(\Rightarrow B=6800\)

B = (-25)68 + (-34)(-250)

    = -25.34.2 - 34(-250)

    = 34(-50 + 250)

    = 34.200

    = 6800