D) 86.56:x-23=665

4816:x=665+23

4816:x=688

x=4816:688

x=7

C) 85.4-x:5=339,4

340-x:5=339,4

-x:5=339,4-340

-x:5=-0,6

x:5=0,6

x=0,6.5

x=3

(111 + 222 + 333 + 444 + 555 + 666 + 777 + 888 + 999)x 2.................999 x 2 x 2 x 2 ?

A.(111 + 222 + 333 + 444 + 555 + 666 + 777 + 888 + 999)x 2 > 999 x 2 x 2 x 2 = 9990 > 7992

B.(111 + 222 + 333 + 444 + 555 + 666 + 777 + 888 + 999)x 2 < 999 x 2 x 2 x 2 = 9990 < 7992

C.(111 + 222 + 333 + 444 + 555 + 666 + 777 + 888 + 999)x 2 = 999 x 2 x 2 x 2 = 9990 = 7992

Đáp án A nhé

(111 + 222 + 333 + 444 + 555 + 666 + 777 + 888 + 999)x 2.................999 x 2 x 2 x 2 ?

A.(111 + 222 + 333 + 444 + 555 + 666 + 777 + 888 + 999)x 2 > 999 x 2 x 2 x 2 = 9990 > 7992

B.(111 + 222 + 333 + 444 + 555 + 666 + 777 + 888 + 999)x 2 < 999 x 2 x 2 x 2 = 9990 < 7992

C.(111 + 222 + 333 + 444 + 555 + 666 + 777 + 888 + 999)x 2 = 999 x 2 x 2 x 2 = 9990 = 7992

minh@@22@22222@@@@? 

\(\left(x+3\right)\left(x^2-3x+9\right)-x\left(x^2-9\right)=27\\ x.x^2-x.3x+x.9-x.x^2+x.9=27\\ x^3-3x^2+9x-x^3+9x=27\\ 3x^2+18x=27\\ 21x^2=27\\ x^2=\dfrac{9}{7}\\ \Rightarrow x=\sqrt{\dfrac{9}{7}}\)

\(\left(x+3\right)\left(x^2-3x+9\right)-x\left(x^2-9\right)=27\\ x.x^2-x.3x+x.9+3.x^2-3.3x+3.9-x.x^2+x.9=27\\ x^3-3x^2+9x+3x^2-9x+27-x^3+9x=27\\ 9x+27=27\\ 9x=0\\ x=0\)

\(1.x-\dfrac{2}{3}\times\left(x+9\right)=1\)

\(x-\dfrac{2}{3}\times x-6=1\)

\(x\times\left(1-\dfrac{2}{3}\right)=7\)

\(x\times\dfrac{1}{3}=7\)

\(x=21\)

\(2.x-\dfrac{11}{15}=\dfrac{3+x}{5}\)

\(\dfrac{15x}{15}-\dfrac{11}{15}=\dfrac{9+3x}{15}\)

\(15x-11=9+3x\)

\(12x=20\)

\(x=\dfrac{5}{3}\)

Thiếu đề rồi bạn

\(\dfrac{x}{x^2-9}+\dfrac{2}{x^2+6x+9}=\dfrac{x\left(x+3\right)+2\left(x-3\right)}{\left(x-3\right)\left(x+3\right)^2}\\ =\dfrac{x^2+5x-6}{\left(x-3\right)\left(x+3\right)^2}=\dfrac{\left(x-1\right)\left(x+6\right)}{\left(x-3\right)\left(x+3\right)^2}\)

13B 14D

Câu 13. Tìm x biết  4x + 12 = 48, ta được x bằng:

A.32                                      B.9                         C.15                       D.54

Câu 14. Tìm x biết  2346 : (x + 8) = 23, ta được x bằng:

A.110                                    B.92                       C.93                       D.94

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