= 4/5 - 9/16.4/5

= 4,5.(1-9/16)

= 4,5. 7/16

= 7/20

\(\dfrac{4}{5}-\dfrac{3}{4}.\dfrac{4}{5}.\dfrac{3}{4}\)

\(=\dfrac{4}{5}-\dfrac{9}{20}\)

\(=\dfrac{16}{20}-\dfrac{9}{20}\)

\(=\dfrac{7}{20}\)

= 4/5 - 9/20

= 16/20 - 9/20

= 7/20

tính bằng cách thuận tiện nhất

a x 3,7 + a x 5,3 + a = 45

a)2401/81

b)1024

c)125/1

`3x-16:2^3=31`

`=>3x-16:8=31`

`=>3x-2=31`

`=>3x=31+2`

`=>3x=33`

`=>x=11`

__

`2^10:2^8+3[4.7+3.4]`

`=2^2+3[4(3+7)]`

`=4+3[4.10]`

`=4+3.40`

`=4+120`

`=124`

__

`4^6:4^3-2^2 . 2^3`

`=4^3-2^5`

`=64-32`

`=32`

__

`141+2^5 . 2^4-3^1 . 3^2`

`=141+2^9-3^3`

`=141+512-9`

`=644`

__

`x+2^5:2^4=4.4^2`

`=>x+2=4^3`

`=>x=64-2`

`=>x=62`

a, \(\dfrac{x}{3}=\dfrac{8}{12};12:3=4\)\(;8:4=2\)

⇒\(x=\dfrac{2}{3}\)

a: \(\dfrac{x}{3}=\dfrac{8}{12}\)

nên x/3=2/3

hay x=2

b: \(x+\dfrac{1}{15}=\dfrac{1}{3}\)

\(\Leftrightarrow x=\dfrac{1}{3}-\dfrac{1}{15}=\dfrac{5}{15}-\dfrac{1}{15}=\dfrac{4}{15}\)

c: \(x\cdot\dfrac{4}{7}-\dfrac{2}{7}=\dfrac{5}{7}\)

\(\Leftrightarrow x\cdot\dfrac{4}{7}=\dfrac{5}{7}+\dfrac{2}{7}=1\)

hay x=7/4

d: \(\Leftrightarrow x\cdot\dfrac{3}{4}-\dfrac{5}{4}=-\dfrac{1}{2}\)

\(\Leftrightarrow x\cdot\dfrac{3}{4}=-\dfrac{2}{4}+\dfrac{5}{4}=\dfrac{3}{4}\)

hay x=1

1)

a) \(...=4^4-225=256-225=31\)

b) \(...=8.9.5+120=360-120=240\)

c) \(...=3^4-3^3=81-27=54\)

d) \(...=7^2-1=49-1=48\)

2) a) \(...=2^6=64\)

b) \(...=3^{15}:3^{10}=3^5=243\)

c) \(...=3^3-3^3=0\)

d) \(...=6^3+4^5=216+1024=1240\)

1. a) 31

    b) 480

    c) 48

    d) 348

2. a) 64

    b) 243

    c) 0

    d) 1240