Tính nhanh :
( 768 - 39 ) -768
( - 1579 ) - ( 12 - 1579 )
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a) ( 768 - 39 ) - 768
= 768 - 39 - 768
= ( 768 - 768 ) - 39
= 0 - 39
= -39
b) ( -1579 ) - ( 12 - 1579 )
= -1579 - 12 + 1579
= ( 1579 - 1579 ) - 12
= 0 - 12
= -12
a) \(\left(768-39\right)-768=768-39-768=768-768-39=0-39=-39\)
b)\(\left(-1579\right)-\left(12-1579\right)=\left(-1579\right)-12+1579=\left[\left(-1579\right)+1579\right]-12=0-12=-12\)
a. (768 - 39) - 768
= 768 - 39 - 768
= 768 - 768 - 39
= 0 - 39
= -39
b. (-1579) - (12 - 1579)
= (-1579) - 12 + 1579
= [(-1579) + 1579] - 12
= 0 - 12
= -12
a) ( 768 - 39 ) -768
= 768 - 39 - 768
= ( 768 - 768 ) -39
= 0 - 39
= -39
b) ( - 1579 ) - ( 12 - 1579 )
= ( - 1579 ) -12 + 1579
= [ ( -1579 ) + 1579 ] -12
= 0 - 12
= -12
tk mn nha!
B1 :
a, = -2-2-2= -6
b, = -2-2-2 = -6
B2:a, = 768-39-768 = (768-768)-39=0-39=-39
b, = -1579-12+1579 = (-1579+1579)-12 = 0-12=-12
k mk nha
a. (768-39)-768
= 768-39-768
= (768-768)-39
= 0-39=-39
b. (-579)-(12-1579)
= -579-12+1579
= (1579-579)-12
= 1000-12=988.
( -1579 ) – ( 12 – 1579 )
= -1579 + 1579 – 12
= 0 – 12
= - 12
\(3)1579-(53+1579)-(53) \)
\(=1579-53-1579+53\)
\(=(1579-1579)-(-53+53)\)
\(=0-0\)
\(=0\)
\(4)2001-15+54-2001-54\)
\(=(2001-2001)+(54-54)-15\)
\(=0+0-15\)
\(=0-15\)
\(=-15\)
\(\dfrac{3}{2}xD=1+\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+...+\dfrac{1}{256}\)
Đặt
\(A=1+\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+...+\dfrac{1}{256}\)
\(2xA=2+1+\dfrac{1}{2}+\dfrac{1}{4}+...+\dfrac{1}{128}\)
\(A=2xA-A=2-\dfrac{1}{256}=\dfrac{511}{256}=\dfrac{3}{2}xD\)
\(\Rightarrow D=\dfrac{511}{256}:\dfrac{3}{2}\)
-39
-12
tick nha
=(768-768)-39=0-39=-39
=(-1589)-(-157)-12=0-12=-12