bài 3: tính nhanh
a) 1/3 -3/4 -(-3/5) + 1/64 – 2/9 – 1/36 + 1/15
b) P= 1/99 – 1/99.98 – 1/98.97 – 1/97.96-….- 1/3.2 – 1/2.1
giúp mk vs mai mk nop roi
bài 3: tính nhanh a) 1/3 -3/4 -(-3/5) + 1/64 – 2/9 – 1/36 + 1/15 b) P= 1/99 – 1/99.98 – 1/98.97 – 1/97.96-….- 1/3.2 – 1/2.1 giúp mk vs mai mk nop r
By Peyton
`a)1/3 – 3/4 – (-3/5) + 1/(64) – 2/9 – 1/(36) + 1/(15)`
`=(1/3 + 3/5 + 1/(15)) – (3/4 + 2/9 + 1/(36)) + 1/(64)`
`=(5/(15) + 9/(15) + 1/(15)) – ((27)/(36) + 8/(36) + 1/(36)) +1/(64)`
`=1/(64)`
`b)P=1/(99 )- 1/(99.98) – 1/(98.97) – 1/(97.96) -…..- 1/(3.2) – 1/(2.1)`
`P=1/(99) – (1/(2.3) + 1/(1.2 )+……+ 1/(97.98) + 1/(98.99))`
`P=1/(99 )- (1 – 1/2 + 1/1 – 1/3 +……+ 1/(98) – 1/(98 )+ 1/(98 )- 1/(99))`
`P=1/(99) – (1- 1/(99))`
`P=(-97)/(99)`
Đáp án:
Giải thích các bước giải:
a)1/3 – 3/4 – (-3/5) + 1/64 – 2/9 – 1/36 + 1/15
=(1/3 + 3/5 + 1/15) – (3/4 + 2/9 + 1/36) + 1/64
=(5/15 + 9/15 + 1/15) – (27/36 + 8/36 + 1/36) +1/64
=1 – 1 + 1/64
=0 + 1/64
=1/64
b)P=1/99 – 1/99.98 – 1/98.97 – 1/97.96 -…..- 1/3.2 – 1/2.1
P=1/99 – (1/2.3 + 1/1.2 +……+ 1/97.98 + 1/98.99)
P=1/99 – (1 – 1/2 + 1/1 – 1/3 +……+ 1/98 – 1/98 + 1/98 – 1/99)
P=1/99 – (1- 1/99)
P=1/99 – 98/99
P=-97/99