ko bit

a, 20^2 - 6^ 2=  400 - 36 = 364

b,3^3 . 18 - 3^3 . 12 = 3^3 . ( 18-12) = 27 . 6 = 162

c, 39 . 213 + 87 . 39 = ( 213 + 87) . 39 = 300 . 39 = 110700

d, 80 - [ 130 - ( 12 - 4)^2] = 80 - [130 - (3^2) ] = 80 - 130 - 9 = -59

tiểu học mà bảo toán lớp 8

bạn đã suy nghĩ chưa

Bạn ghi lại đề bằng công thức đi bạn

\(\left(5^2\times2^3-7^3\times2\right)\div2\times6-7\div2^5\)

\(=\left(25\times8-343\times2\right)\div2\times6-7\div32\)

\(=\left(200-686\right)\div2\times6-7\div32\)

\(=-486\div2\times6-7\div32\)

\(=-1458-0,21875\)

\(=-1458,21875\)

rút gọn

mk lớp 5

co ai giai dc ko cau 60 % .....

$\textbf{Ta có:}$

$A=\dfrac{-5^2-5\cdot3^2}{5^3+5^2\cdot3^2}$

$=\dfrac{-25-45}{125+225}$

$=\dfrac{-70}{350}$

$=-\dfrac15.$

Và

$B=\dfrac{2^{12}\cdot3^{10}+6^9\cdot120}{2^{12}\cdot3^{12}-2^{11}\cdot3^{11}}$

$=\dfrac{2^{12}3^{10}+2^{12}3^{10}\cdot5}{2^{11}3^{11}(2\cdot3-1)}$

$=\dfrac{2^{12}3^{10}(1+5)}{2^{11}3^{11}\cdot5}$

$=\dfrac{2^{12}3^{10}\cdot6}{2^{11}3^{11}\cdot5}$

$=\dfrac{2^2}{5}$

$=\dfrac45.$

=> $M=B-A$$=\dfrac45-\left(-\dfrac15\right)$

$=\dfrac55$$=1.$

5ˣ⁺¹ - 5ˣ = 100 . 25²⁹

5ˣ.(5 - 1) = 100 .(5²)²⁹

5ˣ.4 = 100.5⁵⁸

5ˣ = 100 . 5⁵⁸ : 4

5ˣ = 25 .5⁵⁸

5ˣ = 5².5⁵⁸

5ˣ = 5⁶⁰

x = 60

\(5^{x+1}-5^x=100\cdot25^{29}\\\Rightarrow 5^x\cdot5-5^x=2^2\cdot5^2\cdot(5^2)^{29}\\\Rightarrow 5^x\cdot(5-1)=4\cdot 5^2\cdot5^{58}\\\Rightarrow 4\cdot5^x=4\cdot 5^{60}\\\Rightarrow5^x=5^{60}\\\Rightarrow x=60\\Vậy:x=60\)