72 : (2 x 4) = 72 : 8 = 9

64 : (8 : 4) = 64 : 2 = 32

127/128

      \(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}+\frac{1}{128}\)

\(=\frac{1x64}{2x64}+\frac{1x32}{4x32}+\frac{1x16}{8x16}+\frac{1x8}{16x8}+\frac{1x4}{32x4}+\frac{1x2}{64x2}+\frac{1}{128}\)

\(=\frac{64}{128}+\frac{32}{128}+\frac{16}{128}+\frac{8}{128}+\frac{4}{128}+\frac{2}{128}+\frac{1}{128}\)

\(=\left(\frac{64}{128}+\frac{1}{128}\right)+\left(\frac{32}{128}+\frac{8}{128}\right)+\left(\frac{16}{128}+\frac{4}{128}\right)\)

\(=\frac{65}{128}+\frac{40}{128}+\frac{20}{128}\)

\(=125\)

nhầm , phải bằng\(\frac{125}{128}\)mới đúng

(cách làm ở dưới)

   \(1-\frac{1}{2}-\frac{1}{4}-\frac{1}{8}-\frac{1}{16}-\frac{1}{32}\)\(-\frac{1}{64}\)

\(=1-\frac{32}{64}-\frac{16}{64}-\frac{8}{64}-\frac{4}{64}\)\(-\frac{2}{64}-\frac{1}{64}\)

  \(=1-\left(\frac{32}{64}-\frac{16}{64}-\frac{8}{64}-\frac{4}{64}-\frac{2}{64}-\frac{1}{64}\right)\)

\(=1-\frac{1}{64}\)

\(=\frac{64}{64}-\frac{1}{64}\)

\(=\frac{63}{64}\)

= 1/64 nha

1- 1/2 - 1/4 - 1/8 - 1/16 - 1/32 - 1/64 = 1/64

Bài làm:

Ta có: \(A=64-\left(x-4\right)\left(x^2+4x+16\right)\)

\(A=64-x^3+64\)

\(A=128-x^3\)

Tại \(x=-\frac{1}{2}\) ta được:

\(A=128-\left(-\frac{1}{2}\right)^3=\frac{1025}{8}\)

A = 64 - ( x - 4 )( x² + 4x + 16 )

A = 64 - ( x³ + 4x² + 16x - 4x² - 16x - 64 )

A = 64 - ( x³ - 64 )

A = 64 - x³ + 64

A = -x³ + 128

Thế x = -1/2 vào A ta được :

A = -(-1/2)³ + 128 = 1/8 + 128 = 1025/8

\(A=64-\left(x-4\right)\left(x^2+4x+16\right)\)

\(=64-\left(x-4\right)\left(x^2-4x+4^2\right)\)

\(=64-\left(x^3-4^3\right)=64-x^3+4^3\)

\(=64+64-x^3=128-x^3\)

Với \(x=-\frac{1}{2}\)thì \(128-x^3=128-\left(-\frac{1}{2}\right)^3\)

\(=128-\left(-\frac{1}{8}\right)=128+\frac{1}{8}=\frac{1025}{8}\)

`9 xx ( 175 -63)`

`=9 xx112`

`=1008`

`----`

`(16 + 64):4 xx 2`

`= 80:4 xx 2`

`= 20 xx 2`

`=40`

a)\(9\times\left(175-63\right)\)
\(=9\times112\)
\(=1008\)
b)\(\left(16+64\right):4\times2\)
\(=80:4\times2\)
\(=20\times2\)
\(=40\)

\(a,9.\left(175-63\right)\)

\(=9.112\)

\(=1008\)

\(b,\left(16+64\right):4.2\)

\(=80:4.2\)

\(=20.2\)

\(=40\)

1*2*3*4*5*6*7+64:8

=5040+8=

=5048

k nhe!

5048

k nhé

Vậy tích trên được rút gọn :

1 x 2 x 3 x 4 x 5 x 6 x 7 + 64 : 8 )

= 1 x 2 x 3 x 4 x 5 x 6 x 7 + 8

= 2 x 3 x 4 x 5 x 6 x 7 + 8

= 6 x 4 x 5 x 6 x 7 + 8

= 24 x 5 x 6 x 7 + 8

=120 x 6 x 7 +8

=720 x 7 + 8 

=5040 + 8

=5048

Lời giải:

$T=(x+4)(x^2-4)(x+8)+8(x+3)^2$

$=(x+4)(x+2)(x-2)(x+8)+8(x+3)^2$

$=(x^2+6x+8)(x^2+6x-16)+8(x^2+6x+9)$

$=(a+8)(a-16)+8(a+9)$ (đặt $a=x^2+6x$)

$=a^2-56=(x^2+6x)^2-56\geq 0-56=-56$

Vậy $T_{\min}=-56$. Giá trị này đạt tại $x^2+6x=0\Leftrightarrow x=0$ hoặc $x=-6$