Question

Tìm x :
3+24=51
2 -5 = 44
x-1 = 24 - [ 4²- (2²-1 )]
25 va 7²⁰
30 va 4³⁴
34+5³⁵+5³⁶ va 5³⁷
Cho A = 1+3+3²+3³⁺3⁴+.......3⁹⁹
A
50
x+2 -1
 

Answer 1

Bài 1:

c ) 15 ( 7-x ) =15

=>7-x=1

=>x=6

d ) 34 ( x-3 ) =0

=>x-3=0

=>x=3

e ) 24+6 ( 3-x ) =30

=>6 ( 3-x )=6

=>3-x=1

=>x=2

f )x³+24=51

=>x³=27

=>x³=3³

=>x=3

g ) ( x-5 ) ² -5 = 44

=>(x-5)²=49

=>(x-5)²=7² hoặc (-7)²

=>x-5=7 hoặc (-7)

Với x-5=7 =>x=12Với x-5=-7 =>x=-2

 i ) 3+2^x-1 = 24 - [ 4²- (2²-1 )]

=>3+2^x-1=24- [ 4²- (2²-1 )]

=>3+2^x-1=24-[16-3]

=>3+2^x-1=24-13

=>3+2^x-1=11

=>2^x-1=8

=>2^x-1=2³

=>x-1=3

=>x=4

Bài 3:

a)3A=3(1+3+3²+3³+...3⁹⁹)

3A=3+3²+...+3¹⁰⁰

3A-A=(3+3²+...+3¹⁰⁰)-(1+3+3²+3³+...3⁹⁹)

2A=3¹⁰⁰-1

A=\(\frac{3^{100}-1}{2}\)

b) Ta có:

2A=(3²)⁵⁰-1=9⁵⁰-1<9⁵⁰

c)Thay 2A=3¹⁰⁰-1 vào ta có:

3¹⁰⁰-1=9^x+2 -1

=>(3²)⁵⁰=9⁵⁰-1=9^x+2-1

=>9⁵⁰=9^x+2=>

50=x+2<=>x=48