\(60\%x+\dfrac{2}{3}x=-76\)

\(\dfrac{3}{5}x+\dfrac{2}{3}x=-76\)

\(x\left(\dfrac{3}{5}+\dfrac{2}{3}\right)=-76\)

\(x\dfrac{19}{15}=-76\)

\(x=-76:\dfrac{19}{15}\)

\(x=-60\)

\(60\%x+\dfrac{2}{3}x=-76\)

\(\dfrac{3}{5}x+\dfrac{2}{3}x=-76\)

\(x.\left(\dfrac{3}{5}+\dfrac{2}{3}\right)=-76\)

\(x.\dfrac{19}{15}=-76\)

\(x=-76:\dfrac{19}{15}\)

\(x=-76.\dfrac{15}{19}\)

\(x=-60\)

`60% x+2/3x=-76`

`3/5x+2/3x=-76`

`(3/5+2/3)x=-76`

`19/15x=-76`

`x=-76:19/15`

`x=-60`

2/(11x13) = 1/11 - 1/13 ; 2/(13x15) = 1/13 - 1/15 ; 2/(15x17) = 1/15 - 1/17 ; 2/(17x19) = 1/17 - 1/19 ; 2/(19x21) = 1/19 - 1/21

2/(11x13) + 2/(13x15) + 2/(15x17) + 2/(17x19) 2/(19x21) =

1/11 - 1/13 + 1/13 - 1/15 + 1/15 - 1/17 + 1/17 - 1/19 + 1/19 - 1/21 = 1/11 - 1/21 = 101231

Hay:   10/231 x 462 - X = 19

20 - X = 19

X = 20 - 19

X = 1,đó là phần b

3/5x+2/3x=-76 <=> 19/15x=-76 <=> x=-60,đó là phần a

Bài 1: 

\(101\cdot125+101\cdot25-101\cdot50\)

\(=101\cdot\left(125+25-50\right)\)

\(=101\cdot100\)

\(=10100\)

Bài 2: 

\(76\cdot115+56\cdot24+59\cdot24\)
\(=76\cdot115+24\cdot\left(56+59\right)\)

\(=76\cdot115+24\cdot115\)

\(=115\cdot\left(76+24\right)\)

\(=115\cdot100\)

\(=11500\)

5:

a: =>15x=165

=>x=11

b: =>x(x+1)/2=55

=>x^2+x=110

=>x=10

4: =>7x=56

=>x=8

Bài 1:

101•125+101•25+101•50

= 101•(125+25-50)

=101•100

=10100

Bài 2:

76•115+56•24+59•24

= 76•115+24•(56+59)

= 76•115+24•115

= 115•(76+24)

= 115•100

= 11500

1/3x + 3/4x - 75% = -5 1/4

=> x - 3/4 = -21/4

=> x = -21/4 + 3/4

=> x = -9/2

60%x + 5/6x = -76

=> 3/5x + 5/6x = -76

=> 43/30x = -76

=> x = -76 : 43/30

=> x = -2280/43

\(\frac{1}{3}x+\frac{3}{4}x-75\%=-5\frac{1}{4}\)

\(\frac{13}{12}x-\frac{3}{4}=-\frac{21}{4}\)

\(\frac{13}{12}x=-\frac{9}{2}\)

\(x=-\frac{54}{13}\)

\(60\%.x+\frac{2}{3}x=-76\)

\(\frac{3}{5}x+\frac{2}{3}x=-76\)

\(\frac{19}{15}x=-76\)

\(x=-60\)

\(\frac{x-96}{2}+\frac{x-88}{4}+\frac{x-76}{6}+\frac{x-60}{8}=14\)

\(\frac{x-96}{2}-2+\frac{x-88}{4}-3+\frac{x-76}{6}-4+\frac{x-60}{8}-5=0\)

\(\frac{x-96}{2}-\frac{4}{2}+\frac{x-88}{4}-\frac{12}{4}+\frac{x-76}{6}-\frac{24}{6}+\frac{x-60}{8}-\frac{40}{8}=0\)

\(\frac{x-96-4}{2}+\frac{x-88-12}{4}+\frac{x-76-24}{6}+\frac{x-60-40}{8}=0\)

\(\frac{x-100}{2}+\frac{x-100}{4}+\frac{x-100}{6}+\frac{x-100}{8}=0\)

\((x-100)\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{6}+\frac{1}{8}\right)=0\)

\(\Rightarrow x-100=0\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{6}+\frac{1}{8}>0\right)\)

\(\Rightarrow x=100\)

Bài 1:

a. $=(-25)(-4)(-35)=100(-35)=-3500$

b. $=16-10=6$

c. $=180-(-16)-(-36)=180+16+36=232$

d. $=250-200:[1(-3)^2+(-8)]$

$=250-200:(9-8)=250-200=50$

2.

$60+2(12-x)=-48$

$2(12-x)=60-(-48)=60+48=108$

$12-x=108:2=54$

$x=12-54=-42$
 

Bài 3:

$A=(7+7^2)+(7^3+7^4)+....+(7^{17}+7^{18})$

$=7(1+7)+7^3(7+1)+...+7^{17}(1+7)$

$=(1+7)(7+7^3+....+7^{17})=8(7+7^3+....+7^{17})\vdots 8$

b.

$A=(7+7^2+7^3)+(7^4+7^5+7^6)+...+(7^{16}+7^{17}+7^{18})$

$=7(1+7+7^2)+7^4(1+7+7^2)+....+7^{16}(1+7+7^2)$

$=(1+7+7^2)(7+7^4+....+7^{16})$

$=57(7+7^4+...+7^{16})\vdots 57$

c.

$A=(7+7^2+7^3+7^4)+(7^5+7^6+7^7+7^8)+(7^9+7^{10}+7^{11}+7^{12})+(7^{13}+7^{14}+7^{15}+7^{16})+(7^{17}+7^{18})$
$=7(1+7+7^2+7^3)+7^5(1+7+7^2+7^3)+7^9(1+7+7^2+7^3(+7^{13}(1+7+7^2+7^3)+7^{17}(1+7)$

$=(1+7+7^2+7^3)(7+7^5+7^9+7^{13})+8.7^{17}$

$=400(7+7^5+7^9+7^{13})+8.7^{17}$

Ta thấy $400(7+7^5+7^9+7^{13})\vdots 50$ nhưng $8.7^{17}\not\vdots 50$ nên $A\not\vdots 50$

Bài 1:

a. $=(-25)(-4)(-35)=100(-35)=-3500$

b. $=16-10=6$

c. $180-(-16)-(-36)=180+16+36=196+36=232$

d. $=250-200:[2000.(-3).2-6]$

$=250-200:[2000.(-6)+(-6)]$

$=250-200:[(-6)(2000+1)]=250-200[(-6).2001]$

$=250+200.6.2001=250+2401200=2401450$

Bài 2:

$60+2(12-x)=-48$

$2(12-x)=-48-60=-108$
$12-x=-108:2=-54$

$x=12-(-54)=66$

Bài 3:

Số số hạng của A: $(718-71):1+1=648$

$A=(718+71)\times 648:2=789\times 324$

a. Có: $A=789\times 324=789\times 81\times 4$

$\Rightarrow A\not\vdots 8$ (bạn xem lại đề)

b. $A=789\times 81\times 4\not\vdots 57$ (bạn xem lại đề)

c. $A=789\times 81\times 4\not\vdots 50$ 

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