ax6+a=420

ax=420

a=420:7

a=60 k nha mình k lại

\(a\times6+a=420\)

\(\Leftrightarrow a\times\left(6+1\right)=420\)

\(\Leftrightarrow a\times7=420\)

\(\Leftrightarrow a=\frac{420}{7}=60\)

     Vậy \(a=60\)

a x 6 + a = 420

    a x 7   = 420

         a    = 420 : 7 

         a    = 60

bạn k mình nha

chúc bạn học tốt

`420:a+72:6=18`

`=>420:a+12=18`

`=>420:a=18-12`

`=>420:a=6`

`=>a=420:6`

`=>a=70`

`a+a+a+a+axx2=6630`

`=>a xx (1+1+1+1+2)=6630`

`=> a xx 6=6630`

`=>a=6630:6`

`=>a=1105`

s.o.s

$420:a+72:6=18$

$=>420:a+12=18$

$=>420:a=18-12$

$=>420:a=6$

$=>a=420:6$

$=>a=70$

$a+a+a+a+axx2=6630$

$=>axx(1+1+1+1+2)=6630$

$=>axx6=6630$

$=>a=6630:6$

$=>a=1105$

=x*10-(1+2+3+4+......+10)=145

=x*10-55=145

=x*10=145+45

x*10=200

x=200/10

x=20

b,2.(1+2+3+4+.......+x)=420

1+2+3+4+.....+x=420/2

1+2+3+4+.....+x=210

ta co: 20.21=420

suy ra x=20

t i c k nha ban

Thực hiện phép tính nhé

chabbyhgwwwwwwwwwertyuiopasdfghjkl;zxcvb

ĐON GIAN

a; (2 + 4+ 6 + 8 +...+ 98) x (210 x 12 + 420 - 420 x 7)

= (2 + 4 + 6 + 8 +..+ 98) x (210 x 2 x 6 + 420 - 420 x 7)

= (2 + 4 + 6 + 8 +...+ 98) x (420 x 6 + 420 - 420 x 7)

= (2 + 4 + 6 + 8+...+ 98) x [420 x (6 + 1  - 7)]

= (2 + 4 + 6 +...+ 98) x {420 x 0]

= (2 + 4 + 6 +...+ 98) x 0

= 0 

b; 29 + 299 + 2999 + 29999 + 2999999 

= 30 - 1 + 300 - 1 + 3000 - 1 + 30000 -  1+ 300000 - 1

= (30 + 300 + 3000 + 30000+ 300000) - (1 + 1 + 1 + 1 + 1)

= 333330 - 5

= 333325

c; 1999 x 1867 + 2000 x 133

= (2000 - 1) x 1867 + 2000 x 133

= 2000 x1867 - 1867 + 2000 x 133

= (2000 x 1867 + 2000 x133) - 1867

= 2000 x ( 1867 + 133)  - 1867

= 2000 x 2000 -  1867

= 4000000 - 1867

= 3998133

a)\(2.x-138=8.9\)

\(2.x-138=72\)

\(2.x=72+138\)

\(2.x=210\)

\(x=210\div2\)

\(x=105\)

b)\(\left\{\left(6x-72\right)\div2-84\right\}.28=5628\)

\(\left(6x-72\right)\div2-84=201\)

\(\left(6x-72\right)\div2=285\)

\(6x-72=570\)

\(6x=642\)

\(x=107\)

c)\(420+65.4=\left(x+175\right)\div5+30\)

\(420+260=\left(x+175\right)\div5+30\)

\(680=\left(x+175\right)\div5+30\)

\(650=\left(x+175\right)\div5\)

\(3250=x+175\)

\(3075=x\)

a) 2 * x - 138 = 72

    2 * x          = 72 + 138

    x                = 210 \ 2

    x                = 105

Mk thay x=y nha!!!

a)2xy-138=8x9

2xy-138=72

2xy=72+138

2xy=210

y=210:2

y=105

b){(6xy-72):2-84)}x28=5628

{(6xy-72):2-84)}x28=5628

{(6xy-72):2-84=201

{(6xy-72):2=285

(6xy-72)=570

6y=570+72

6y=642

=>y=107

c)420+65x4=(y+175):5+30

680=(y+175):5+30

650=(y+175):5

3250=y+175

y=3250-175

y=3075

\(Tacó:\)

\(xy=6.UCLN\left(x,y\right)=1\)

\(\Leftrightarrow6=xy=2.3=3.2=1.6=6.1\)

\(+xy=2.3\Rightarrow\left(x,y\right)=1\left(tm\right).Th:xy=3.2\left(tm\right)\)

\(+xy=1.6=6.1\Rightarrow\left(x,y\right)=1\left(tm\right)\)

\(\Rightarrow x,y\in\left\{\left(1;6\right),\left(6;1\right),\left(2;3\right),\left(3;2\right)\right\}\)

a=18.\(\left\{7+[150-(136-115)\right\}\)

a=18.[ 7+(150-21)

a=18.(7+129)

a=18.136

a=2448

A=18{420:6+[150-(68.2-23.5)]}

A=18{7+[150-(136-115)]}

A=18{7+[150-21]}

A=18{7+129}

A=18.136

A=2448

a)

160 : (4 × 8) = 160 : 32 = 5

160 : 4 : 8 = 40 : 8 = 5

Vậy 160 : (4 × 8) = 160 : 4 : 8.

96 : (3 × 8) = 96 : 24 = 4

96 : 3 : 8 = 32 : 8 = 4

Vậy 96 : (3 × 8) = 96 : 3 : 8.

105 : (5 × 7) = 105 : 35 = 3

105 : 5 : 7 = 21 : 7 = 3

Vậy 105 : (5 × 7) = 105 : 5 : 7.

Nhận xét: a : (b × c) = a : b : c

b)

270 : (9 × 6) = 270 : 9 : 6 = 30 : 6 = 5

420 : (7 × 3) = 420 : 7 : 3 = 60 : 3 = 20

144 : (2 × 8) = 144 : 2 : 8 = 72 : 8 = 9