15+35+55+75+95+105+115

=495

chuc bn hoc gioi!

nhae

~~~~~~~~~

15 + 35 + 55 + 75 + 95 + 105 + 115 = 495

k mk , mk k lại

kết quả là 495

a) \(105^3-15.105^2+75.105-125\)

\(=105^3-3.105^2.5+3.105.5^2-5^3\)

\(=\left(105-5\right)^3\)

\(=100^3=1000000\)

b) \(63^2-27^2+72^2-18^2\)

\(=\left(63-27\right)\left(63+27\right)+\left(72-18\right)\left(72+18\right)\)

\(=36.90+54.90\)

\(=90.90=8100\)

A= 1000000

B=8100

a) 

= \(105^3-3\cdot105^2\cdot5+3\cdot105\cdot5^2-5^3\)    

= \(\left(105-5\right)^3\) 

\(=100^3=1000000\)          

b) 

= \(\left(63-27\right)\left(63+27\right)+\left(72-18\right)\left(72+18\right)\) 

= \(36\cdot90+54\cdot90\) 

= \(90\left(36+54\right)\)                

\(=90\cdot90\)    

\(=90^2=8100\)

Tính nhanh:

     9 x 8 x 5 + 15 x 3 x 71 + 45

= 45 x 8 + 45 x 71 + 45

= 45 x ( 8 + 71 + 1 )

= 45 x 80

= 3600

 Tính tổng:

A = 115 + 110 + 105 + ... + 20 + 15

A= ( 15 + 115 ) x [ ( 115 - 15 ) : 5 + 1 ] 

A = 130 x 21

A = 2730

B = 99 - 97 + 95 - 93 + ... + 51 - 49

B = ( 99 - 97 ) + ( 95 -93 ) +...+ ( 51 - 49 )

B = 2 + 2 +...+ 2

B = 2 x 26

B = 52

C= 31 + 34 + 37 +...+ 91

C= ( 91 + 31 ) x [ ( 91 - 31 ) : 3 + 1 ]

C= 122 x 21

C= 2562

Số a là : 115 : 5 x 30 = 690

Đ/S : a = 690 .

2:

a: 27(x-45)=0

=>x-45=0

=>x=45

b: (x-47)-115=0

=>x-47=115

=>x=162

d: x-105:21=15

=>x-5=15

=>x=20

1:

a: =35*(34+86)+65*(75+45)

=120*35+120*65

=120*100=12000

b: \(=39\left(53+47\right)-21\left(53+47\right)\)

=18*100=1800

105+(75-105)-(-100+75)
=105+75-105+100-75
=(105-105)+(75-75)+100
=0+0+100
=100

= 105 +(75 -105 ) - (100 + 75)

=105 + 75 - 105  + 100 - 75

= (105 - 105 ) + (75 -75) +100

=0 + 0 + 100

=100

                                CHÚC BN HOK TỐT NHỚ K VHO MIK NHÉ~~~~

= 105 + 75 - 105 - 100 + 75

= (105 - 105) + (75 -75) +100

= 0 + 0 + 100

= 100

=(5.18-5.105)-(105.8-5.105)

=5.18-5.105-105.5+5.105

=(5.18-18.108)+(5.105-105.5)

=18(5-105)+0

=18(-100)

=-1800

=5.18+105-105.18+5

=18 (5+5+105+105)

=18.220

=3960

tick nha milk đang cần