`1 - (5 4/9 + x - 7 7/8) : 15 3/4 = 0`

`1 - (49/9 + x - 63/8) : 63/4 = 0`

`(49/9 + x - 63/8) : 63/4 = 1-0`

`(49/9 + x - 63/8) : 63/4 = 1`

`49/9 + x - 63/8=1 . 63/4`

`49/9 + x - 63/8=63/4`

`49/9 + x = 63/4 + 63/8`

`49/9  +x = 126/8 + 63/8`

`49/9 + x =189/8`

`x=189/8 - 49/9`

`x = 1309/72`

Vậy `x = 1309/72`

\(\left(7^8+7^9+7^{10}\right):7^7\\ =\dfrac{7^8}{7^7}+\dfrac{7^9}{7^7}+\dfrac{7^{10}}{7^7}\\ =7^1+7^2+7^3=399=57\times7⋮57\)

không chia hết cho 57(nghĩa là có dư khi chia cho 57)

Cái cuối cùng là 2015 nha mn giúp mik vs 

\(a^3+b^3+c^3=3abc\)

\(\Leftrightarrow a^3+b^3+c^3-3abc=0\)

\(\Leftrightarrow\left(a+b\right)^3-3ab\left(a+b\right)+c^3-3abc=0\)

\(\Leftrightarrow\left(a+b+c\right)^3-3c\left(a+b\right)\left(a+b+c\right)-3ab\left(a+b+c\right)=0\)

\(\Leftrightarrow\left(a+b+c\right)\left[\left(a+b+c\right)^2-3ab-3bc-3ac\right]=0\)

\(\Leftrightarrow\left(a+b+c\right)\left(a^2+b^2+c^2-ab-bc-ca\right)=0\)

\(\Leftrightarrow\left(a+b+c\right)\left[\left(a-b\right)^2+\left(b-c\right)^2+\left(c-a\right)^2\right]=0\)

mà \(a,b,c\) là các số dương nên 

\(\left(a-b\right)^2+\left(b-c\right)^2+\left(c-a\right)^2=0\)

\(\Leftrightarrow a=b=c\).

Do đó \(M=0\).

help vs mn

Dễ thấy \(x>0\). 

Khi đó \(\left|x+9\right|=x+9,\left|x+6\right|=x+6,\left|x+2021\right|=x+2021\)

\(\left|x+9\right|+\left|x+6\right|+\left|x+2021\right|< 4x\)

\(\Leftrightarrow3x+2036< 4x\)

\(\Leftrightarrow x>2036\)

7^20+7^19-7^18                                                                                        =7^18(7^2+7-1)
=7^18(49+7-1)
=7^18x55
=7^18x11x5 chia hết cho 11                                                                               Vậy......

`x + 6829 = 17939`

`x=17939 - 6829`

`x = 11110`

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`82973 -x = 62838`

`x = 82973 - 62838`

`x = 20135`

___________________

`x : 8 = 1321`

`x = 1321 xx 8`

`x = 10568`

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`x xx 3 + 7270 = 18382`

`x xx 3 = 18382 - 7270`

`x xx3 = 11112`

`x = 11112 : 3`

`x = 3704`