\(a)9.4.25.8.125\)

\(=9.\left(4.25\right).\left(8.125\right)\)

\(=9.100.1000\)

\(=900.1000\)

\(=900000\)

\(a,9.4.25.8.125=9.\left(4.25\right).\left(8.125\right)=9.100.1000=900000\)

\(b,25.5.27.2\)(câu này hình như thiếu đề, ko tính nhanh đc)

\(c,37.7+80.3+43.7\)\(=7.\left(37+43\right)+80.3\)\(=7.80+3.80=80\left(7+3\right)=80.10=800\)

\(d,113.38+113.62+87.62+87.38\)\(=113\left(38+62\right)+87\left(62+38\right)\)

\(=113.100+87.100=100.\left(113+87\right)=100.200=20000\)

Viết gọn lũy thừa:

\(a,x.x.y.y.x.y.x=\left(x.x.x.x\right).\left(y.y.y\right)=x^4.y^4\)

\(b,7^5:343=7^5:7^3=7^{5-3}=7^2\)

\(c,A^{12}:A^{18}=A^{12-18}=A^{-6}\)

\(d,x^7.x^4.x=x^{7+4+1}=x^{12}\)

\(S=1+3^2+3^4+...+3^{2022}\)

\(3^2S=9S=3^2+3^4+3^6+...+3^{2024}\)

\(S=\dfrac{9S-S}{8}=\left(3^{2024}-1\right):8\)

d, không đáp án nào đúng

Lời giải:

$S=1+3^2+3^4+....+3^{2022}$

$9S=3^2S=3^2+3^4+3^6+...+3^{2024}$

$\Rightarrow 9S-S=3^{2024}-1$

$\Rightarrow S=\frac{3^{2024}-1}{8}$

Đáp án D.

a)  \(6^2:4\times3+2\times5^2\)

\(=36:4\times3+2\times25\)

\(=9\times3+50\)

\(=27+50\)

\(=77\)

b)   \(125+70+375+230\)

\(=\left(125+375\right)+\left(70+230\right)\)

\(=500+300\)

\(=800\)

c)   \(150:\left[25\times\left(18-4^2\right)\right]\)

\(=150:\left[25\times\left(18-16\right)\right]\)

\(=150:\left[25\times2\right]\)

\(=150:50\)

\(=3\)

Cảm ơn bạn nhiều

a) 113.38+87.62+113.62+87.38

 =(113.38+87.38)+(87.62+113.62)

 =38.(113+87)+62.(87+113)

 =38.200+62.200

 =200.(38+62)

 =200.100

 =20000

b) 2.125.18+3.12.252+4.223.9

= 2.18.125+3.12.252+4.9.223

=36.125+36.252+36.223

=36.(125+252+223)

=36.500

=18000

Chúc bạn học tốt~~~

a) 5. 4² - 18 : 3² =  5 . 16  -18 : 9 = 80 - 2 = 78

b) 3³ .18 -3³ .12 = 3³ . 6 =  27 .6 = 162

c) 39 . 213 + 87 . 39 = 39 . ( 213 + 87 ) = 39 . 300 = 11700

d) 80 - [ 130 - ( 12 - 4 ) .2 ] = 80 - (130 - 8.2 ) = 80 - 114 = -34

OK

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