\(a.-\dfrac{1}{2}\)

\(b.3\)

\(c.5\)

Ta có 1x2x3x...x9-1x2x3x...x8=1x2x3x...x8x8

Mà 1x2x3x...x8x8-1x2x3x...x8x8=0 

Suy ra 1x2x3x...x9-1x2x3x...x8-1x2x3x...x8x8=0

a) x = 3

b) x = -2

c) x= -8

d) x = -10

e) x= 8 hoặc x = -8

f) x = 11 hoặc x = -11

=362880-40320-5040x8^2

=317520x8^2

=2540160^2

=6452412825600

Tk plz

:))

Thanks

=362880-40320-5040x8^2

=317520x8^2

=2540160^2

=6452412825600

1.2.3...9 - 1.2.3...8 - 1.2.3...8²

= 1.2.3...8.(9 - 1 - 8)

= 1.2.3...8.0

= 0

\(a,12,3\cdot4,7+5,3\cdot12,3-1,4\cdot7,5+7,5\cdot5,4\)

\(=12,3\cdot\left(4,7+5,3\right)-7,5\cdot\left(1,4+5,4\right)\)

\(=12,3\cdot10-7,5\cdot6,8\)

\(=123-51\)

\(=72.\)

\(b,3\cdot x-1=\frac{3}{4}:\frac{15}{16}\)

\(\Leftrightarrow3\cdot x-1=\frac{3}{4}\cdot\frac{16}{15}\)

\(\Leftrightarrow3\cdot x-1=\frac{4}{5}\)

\(\Leftrightarrow3\cdot x=\frac{4}{5}+1\)

\(\Leftrightarrow3\cdot x=\frac{9}{5}\)

\(\Leftrightarrow x=\frac{9}{5}\div3\)

\(\Leftrightarrow x=\frac{9}{5}\cdot\frac{1}{3}\)

\(\Leftrightarrow x=\frac{3}{5}\)

a) \(12,3\times4,7+5,3\times12,3-1,4\times7,5+7,5\times5,4\)

\(=12,3\times\left(4,7+5,3\right)+7,5\times\left(5,4-1,4\right)\)

\(=12,3\times10+7,5\times4\)

\(=123+30\)

\(=153\)

b) \(3.x-1=\frac{3}{4}:\frac{15}{16}\)

\(\Rightarrow3.x-1=\frac{4}{5}\)

\(\Rightarrow3.x=\frac{9}{5}\Rightarrow x=\frac{3}{5}\)

Ta có:  ⇔ x2 = 2.8 = 16 = 42 = (-4)2

Suy ra : x = 4 hoặc x = -4