= 48875

48 x 125 + 875 x 49 

=\(\text{48 x 49 x ( 125 + 875 ) }\)

= \(\text{48 x 49 x 1000}\)

=\(\text{2352 x 1000}\)

=\(\text{2352000}\)

\(\sqrt{49}=7\\ \sqrt{144}=12\\ 100\cdot298=28900\)

48 x 125 + 875 x 49 

48 x 49 x ( 125 + 875 ) 

48 x 49 x 1000

2352 x 1000

2352000

K nha

48 x 125 + 875 x 49

= 48 x 125 + 125 x 7 x 49

= 48 x 125 + 125 x 343

= (48 + 343) x 125

= 391 x 125

= 48875

48 x 125 + 875 x 49

= 48 x 125 + 875 x (48 + 1)

= 48 x 125 + 875 x 48 + 875 x 1

= 48 x (125 + 875) + 875 x 1

= 48 x 1000 + 875

= 48000 + 875 

= 48875

\(\sqrt{\dfrac{49}{100}}=\dfrac{7}{10}\\ \sqrt{\dfrac{144}{289}}=\dfrac{12}{17}\\ \dfrac{\sqrt{36}}{\sqrt{225}}=\dfrac{6}{15}=\dfrac{2}{5}\\ \dfrac{\sqrt{25}}{\sqrt{121}}=\dfrac{5}{11}\)

`\sqrt{49/100}=\sqrt{(7/10)^2}=7/10`

`\sqrt{144/289}=\sqrt{(12/17)^2}=12/17`

`\sqrt{36/225}=\sqrt{(6/15)^2}=6/15`

`\sqrt{25/121}=\sqrt{(5/11)^2}=5/11`

b) Ta có:

Tại x= 5 thì biểu thức P xác định nên giá trị của biểu thức P tại x = 5 là:

\(A=\frac{x^2-49}{-x^2-7x}=\frac{\left(x-7\right)\left(x+7\right)}{-x\left(x+7\right)}=\frac{-x+7}{x}\)

Thay x = 1 vào giá trị biểu thức A ta có :

\(\frac{-1+7}{1}=6\)

(140 x \(\frac{7}{3}\) - 138 x \(\frac{5}{12}\)) : \(\frac{49}{6}\)=

=\(:\frac{49}{6}\)

=  (\(\frac{1960}{6}-\frac{345}{6}\)  ) :\(\frac{49}{6}\)

=\(\frac{1615}{6}:\frac{49}{6}\)

=\(\frac{1615}{49}\)

4x²- 28x+49=(2x)²-2.2x.7+7²=(2x-7)²=(2.4-7)²=1²=1

\(a,=\left(2x-7\right)^2=\left(2.4-7\right)^2=1\)

\(b,\left(x-3\right)^3=\left(5-3\right)^3=8\)

a)   \(4x^2-28x+49\)

\(=\left(2x-7\right)^2\)

\(=\left(2.4-7\right)^2=1\)

b)  \(x^3-9x^2+27x-27\)

\(=\left(x-3\right)^3\)

\(=\left(5-3\right)^3=8\)