12 : {390 : [500 - (125 + 35 . 7)]}

= 12 : {390 : [500 - (125 + 245)]}

= 12 : [390 : (500 - 370)]

= 12 : (390 : 130)

= 12 : 3

= 4

12 : { 390 : [ 500 - ( 125 + 35. 7 ) ] }

   =  12 : { 390 : [ 500 - ( 125 + 245 ) ] }

   =   12 : { 390 : [ 500 - 370 ] }

   =   12 : { 390 : 130 }

    =   12 : 3

    =     4

a) -1816

b) - 700

c)  4800

d) 8

\(44.179+20^2-79.44\\ =44\left(179-79\right)+400\\ =44.100+400\\ =100\left(44+4\right)=4800\\ 3.4^2:\left[500-\left(7.35+125\right)\right]\\ =3.16:\left[500-370\right]\\ =48:130=\dfrac{24}{65}\\ 187+\left[921-\left(921+887\right)\right]\\ =187+921-921-887\\ =187-887=-700\)

44. 179+ 20² - 79.44 3. 4² : [500- (7.35+125)]

= 44. 179+400 - 79.44 = 3. 16: [500- (245+125)]

= 44. (179-79) +400 = 48: [ 500-370 ]

= 44. 100+400 = 48:130

= 4400+400 = 0, 369...

= 4800

187+ [ 921-( 921+887) = 187+ [921- 1808]

= 187+ (-159)

= 28

\(a)44.179+20^2-79.44\)

\(=44.\left(179-79\right)+20^2\)

\(=44.100+400\)

\(=4400+400=4800\)

\(b)3.4^2:\left[500-\left(7.35+125\right)\right]\)

\(=3.4^2:\left[500-\left(245+125\right)\right]\)

\(=3.4^2:\left[500-370\right]\)

\(=3.16:130\)

\(=48:130=\dfrac{24}{65}\)

\(c)187+\left[921-\left(921+887\right)\right]\)

\(=187+\left[921-1808\right]\)

\(=187+\left[921-1808\right]\)

\(=187+\left(-887\right)\)

\(=-700\)

a. \(678\times\left(276+49\right)-678\times\left(149+76\right)\)

\(=678\times\left[\left(276+49\right)-\left(149+76\right)\right]\)

\(=678\times\left(276+49-149-76\right)\)

\(=678\times\left(200-100\right)\)

\(=67800\)

b. \(23\times157+15\times46-28\times87\)

\(=3611+690-2436\)

\(=1865\)

c. \(12:\left\{390:\left[500-\left(125+35\times7\right)\right]\right\}\)

\(=12:\left\{390:\left[500-\left(125+245\right)\right]\right\}\)

\(=12:\left\{390:\left[500-370\right]\right\}\)

\(=12:\left\{390:130\right\}\)

\(=12:3\)

\(=4\)

\(\left(-79\right).\left(8-313\right)-313.79\)

\(=-79.\left(8-313+313\right)\)

\(=-79.8\)

\(=-632\)

\(32.17.\left(-125\right).25.2\)

\(=32.25.\left(-125\right).2.17\)

\(=800.\left(-250\right).17\)

\(=200000.17\)

\(=3400000\)

học tốt

1.

\(\sqrt{a}.\sqrt{\frac{32}{a}}=\sqrt{a.\frac{32}{a}}=\sqrt{32}=\sqrt{4^2.2}=4\sqrt{2}\)

2.

\(\sqrt{3,6a}.\sqrt{10a^3}=\sqrt{3,6a.10a^3}=\sqrt{36a^4}=\sqrt{(6a^2)^2}=6a^2\)

3.

\(\sqrt{0,5a}.\sqrt{50a^3}=\sqrt{0,5a.50a^3}=\sqrt{25a^4}=\sqrt{(5a^2)^2}=5a^2\)

4.

\(\sqrt{2a^3}.\sqrt{50a}=\sqrt{2a^3.50a}=\sqrt{100a^4}=\sqrt{(10a^2)^2}=10a^2\)

5.

\(\sqrt{2}.\sqrt{2+\sqrt{3}}=\sqrt{2(2+\sqrt{3})}=\sqrt{4+2\sqrt{3}}\)

\(=\sqrt{3+2\sqrt{3}+1}=\sqrt{(\sqrt{3}+1)^2}=\sqrt{3}+1\)

\(\sqrt{2}.\sqrt{2-\sqrt{3}}=\sqrt{2(2-\sqrt{3})}=\sqrt{4-2\sqrt{3}}=\sqrt{3-2\sqrt{3}+1}\)

\(=\sqrt{(\sqrt{3}-1)^2}=|\sqrt{3}-1|=\sqrt{3}-1\)

A

A

B

D

B

D

B

C

C

C

A

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