S lớn nhất chia hết cho 5 có 4 CS là : 9995

Số nhỏ nhất  chia 5 có 4CS là : 1000

Số các số chia hết cho 5 là

             (9995-1000):5+1=1800 ( số)

Số các số có 4 CS ko chia hết cho 5 là :

             9999-1800=8199( số)

                    đs : 8199 so

so viet them la 6

k nah!

3kg20g=3,02kg

2,48 lít nước nặng số kg là : 1x2,48=2,48[kg]

chai rỗng cân nặng số kg là : 3,02-2,48=0,54[kg]

đáp số : 0,54 kg

1441,5 nha mọi người đảm bảo 10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000%

and

999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999%

Bài 14:Tìm x

a,\(x-3=\left(3-x\right)^2\)

\(\Rightarrow\left(x-3\right)-\left(3-x\right)^2=0\)

\(\Rightarrow\left(x-3\right)+\left(x-3\right)^2=0\)

\(\Rightarrow\left(x-3\right)\left(1+x-3\right)=0\)

\(\Rightarrow\left(x-3\right)\left(x-2\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}x-3=0\\x-2=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=3\\x=2\end{matrix}\right.\)

b,\(\left(2x-5\right)-\left(5+2x\right)^2=0\)

\(\Rightarrow\left(2x-5\right)+\left(2x-5\right)^2=0\)

\(\Rightarrow\left(2x-5\right)\left(1+2x-5\right)=0\)

\(\Rightarrow\left(2x-5\right)\left(2x-4\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}2x-5=0\\2x-4=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}2x=5\\2x=4\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{5}{2}\\x=2\end{matrix}\right.\)

a= 129.

b=125.

ta có:\(\left(x-y\right)^2+4\left(x-y\right)-12\)

Đặt \(x-y=z\), ta được:

\(z^2+4z-12=z^2+6z-2z-12\)

\(=\left(z^2-2z\right)+\left(6z-12\right)\)

\(=z\left(z-2\right)+6\left(z-2\right)\)

\(=\left(z+6\right)\left(z-2\right)\)

Thay \(z=x-y\) ,ta được:

\(\left(x-y+6\right)\left(x-y-2\right)\)

5+8=13

h minh nha