Question

tính hợp lý nếu có thể

a)78x31+78x68+78

b)1024:(2^2x7+2^2x25)

c)24 - [20 - (5 - 1)^2 ]

tìm x

a)x^3=64

b)2^x+1=128

Answer 1

78.31+78.68+78

=78.31+78.68+78.1

=78.(31+68+1)

=78.100

=7800

1024:(2².7+2².25)

=1024:[2².(7+25)]

=1024:128

=8

24-[20-(5-1)²]

=24-[20-4²]

=24-[20-16]

=24-4

=20

x³=64

=>x³=4³

=>x=4

2^x+1=128

2^x.2¹=128

2^x=128:2

2^x=64

2^x=2⁶

=>x=6

Answer 2

a ) 7800

b) 8

c)20

tim x

a)x=4

b) x = 6

Answer 3

a) 78 x 31 + 78 x 68 + 78

= 78 x ( 31 + 68 + 1 )

= 78 x 110

= 78 x 11 x 10

= 858 x10

= 8580

b) 1024 : ( 2² x 7 + 2²  x 25 )

= 1024 :  [ 2² x ( 7 + 25 ) ]

= 1024 : [ 2² x 32 ]

= 1024 : [ 2² x 2⁵ ]

= 2¹⁰ : 2⁷

= 2³