a)15.(`-2/3`)²-`7/3`
=`20/3`-`7/3`
=`13/3`
b)(`3/7`.`1/2`)²
=`(` `3/14` `)`²
=`9/196`
c)(`3/4`.5`/6`)²
=`(` `5/8` `)`²
=`25/64`
d)5^4.20^4/25^5.4^5
=`(5.20)^4/(25.4)^5`
=100^4/100^5
=`100^-1`
=-0,01
e)`2^4`.8.[(-2)².`1/2`]
=`2^4`.8.(4.`1/2`)
=`2^4`.8.2
=16.8.2
=256
g)(`1/4`)².4+(-2)²
=`1/4`.4+4
=1+4
=5
bài 2:tìm x
a)(x+`1/2`)²=`4/25`
(x+`1/2`)²=(`2/5`)²
x+`1/2`=`2/5`
x=`2/5`-`1/2`
x=`-1/10`
b)`3/4`-2.l2x+`1/3`l=`1/2`
2.l2x+`1/3`l=`3/4`-`1/2`
2.l2x+`1/3`l=`1/4`
l2x+`1/3`l=`1/4`:2
l2x+`1/3`l=`1/8`
⇒l2x+`1/3`l=`1/8` hoặc `-1/8`
Th1:2x+`1/3`=`1/8`
2x+`1/3`=`1/8`
2x=`1/8`-`1/3`
2x=`-5/24`
x=`-5/24`:2
x=`-5/48`
Th2:2x+`1/3`=`-1/8`
2x=`-1/8`-`1/3`
2x=`-11/24`
x=`-11/24`:2
x=`-11/48`
vậy x=`-5/48` hoặc `-11/48`
c)(x-1)^x+2=(x-1)^+6
(x-1)^x+2-(x-1)^x+2=0
(x-1)^x+2.(x-1)^4-(x-1)^x-2=0
(x-1)^x+2.[(x-1)^4-1]=0
Th1:(x-1)^x+2=0
x-1=0
x=0+1
x=1
Th2:(x-1)^4-1=0
(x-1)^4=0+1
(x-1)^4=1
⇒x-1=1 hoặc -1
x-1=1 x-1=-1
x=1+1 x=-1+1
x=2 x=0
vậy x∈ ( 0;1;2 )
