\(\dfrac{31}{48}\times\dfrac{32}{93}\)

\(=\dfrac{31\times32}{48\times93}\)

\(=\dfrac{1\times2}{3\times3}\)

\(=\dfrac{2}{9}\)

============

\(\dfrac{77}{80}\times\dfrac{48}{49}\)

\(=\dfrac{77\times48}{80\times49}\)

\(=\dfrac{11\times3}{5\times7}\)

\(=\dfrac{33}{35}\)

=============

\(\dfrac{154}{125}\times\dfrac{25}{44}\)

\(=\dfrac{154}{125}\times\dfrac{25}{44}\)

\(=\dfrac{7\times1}{5\times2}\)

\(=\dfrac{7}{10}\)

x⁴+4x³-4x²-48x-48=0

=> x⁴+4(x³-x²) - 48x = 48

=> x⁴ + 4[x²(x-1)] - 48x = 48 

     \(x^4+4x^3-4x^2-48x-48=0\)

\(\Leftrightarrow\)\(x^4-2x^3-4x^2+6x^3-12x^2-24x+12x^2-24x-48=0\)

\(\Leftrightarrow\)\(x^2\left(x^2-2x-4\right)+6x\left(x^2-2x-4\right)+12\left(x^2-2x-4\right)=0\)

\(\Leftrightarrow\)\(\left(x^2-2x-4\right)\left(x^2+6x+12\right)\)

\(\Leftrightarrow\)\(\left[\left(x-1\right)^2-5\right]\left(x^2+6x+12\right)=0\)

\(\Leftrightarrow\)\(\left(x-1-\sqrt{5}\right)\left(x-1+\sqrt{5}\right)\left(x^2+6x+12\right)=0\)

Ta có:   \(x^2+6x+12=\left(x+3\right)^2+3>0\)

\(\Rightarrow\)\(\orbr{\begin{cases}x-1-\sqrt{5}=0\\x-1+\sqrt{5}=0\end{cases}}\)      

\(\Leftrightarrow\)\(\orbr{\begin{cases}x=1+\sqrt{5}\\x=1-\sqrt{5}\end{cases}}\)

Vậy...

-48+[48x(-78+-21)]

=-48+48x-99

=48x(-99+-1)

=48x-100

=-4800

- 48 + 48 . ( - 78 ) + 48 . ( - 21 )

= 48. [ -1 + ( - 78 ) + ( - 21 ) ] 

= 48. ( - 100 )

= - 4800 

\(\Delta=b^2-4ac=\left(-48\right)^2-4.1.\left(-25\right)=2400>0\)

do đó pt có 2 nghiệm phân biệt là:

\(•x_1=\dfrac{-b-\sqrt{\Delta}}{2a}=\dfrac{48-\sqrt{2400}}{2}=24-10\sqrt{6}\\ •x_2=\dfrac{-b+\sqrt{\Delta}}{2a}=\dfrac{48+\sqrt{2400}}{2}=24+10\sqrt{6}\)

\(x^2-48x-25=0\)

\(\Leftrightarrow x^2-2.x.24+24^2-601=0\)

\(\Leftrightarrow\left(x-24\right)^2-601=0\)

\(\Leftrightarrow\left(x-24\right)^2=601\)

\(\Leftrightarrow x-24=\sqrt{601}\)

\(\Leftrightarrow\left[{}\begin{matrix}x-24=\sqrt{601}\\x-24=-\sqrt{601}\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=24+\sqrt{601}\\x=24-\sqrt{601}\end{matrix}\right.\)

-48+48.(-78)+48.(-21)

=48.(-1)+48.(-78)+48.(-21)

=48.(-1+(-78)+(-21))

=48.(-100)

=-4800

-48+48x(-78)+48x(-21)=-4800

a, \(49x^2-70x+25=\left(7x\right)^2-2.7x.5+5^2=\left(7x-5\right)^2\)

Thay x = 5 vào biểu thức trên : \(\left(35-5\right)^2=30^2=900\)

b, \(x^3+12x^2+48x+64=\left(x+4\right)^3\)

Thay x = 6 vào biểu thức trên ta được : \(\left(6+4\right)^3=1000000\)

3, \(4x^2+4xy+y^2=\left(2x+y\right)^2\)

Thay x = -6 ; y = 2 vào biểu thức trên ta được : \(\left(-12+2\right)^2=100\)

các bạn ơi

Ví 1 mũ bao nhiêu cũng bằng 1

nên A(x)=50+49+48+47+...+2+1

            =(50+1)+(49+2)+...(17+14)+(16+15)

            =51+51+51+51+......+51+51       (25 số 51)

            =51.25

            =1275

Vậy ......

nhớ tk mình nha

thay x =1 ta được:

\(50.1^{50}+49.1^{49}+48.1^{48}+...+2.1^2+1=>50+49+48+...+2+1=\)(50+1).50:2=1275

nhé bn

   48 - 48 x ( 246 + 54 - 300 )

= 48 - 48 x ( 300 - 300 )

= 48 - 48 x 0

= 48 - 0

= 48

Tk Mình Nha ( MK CHUẨN BỊ LÊN LỚP 6 THUI )

\(48-48.\left(246+54-300\right)\)

\(=48-48\left(300-300\right)\)

\(=48-48.0\)

\(=48-0\)

\(=48\)