\(a,-3^x=81\\ \Leftrightarrow-3^x=\left(-3\right)^4\\ \Leftrightarrow x=4\)

\(b,-3^x=27\\ \Leftrightarrow-3^x=\left(-3\right)^3\\ \Leftrightarrow x=3\)

c, d thiếu đề

a: \(\Leftrightarrow x=4\)

b: x=3

a)\(\left(\frac{3}{5}\right)^5\times x=\left(\frac{3}{7}\right)^7\)

\(\Leftrightarrow\frac{3^5}{5^5}\times x=\frac{3^7}{7^7}\)

\(\Leftrightarrow x=\frac{3^7}{7^7}:\frac{3^5}{5^5}\)

\(\Leftrightarrow x=\frac{3^7\times5^5}{7^7\times3^5}\)

\(\Leftrightarrow x=\frac{3^2\times5^5}{7^7}\)

b)\(\left(\frac{-1}{3}\right)^3\times x=\frac{1}{81}\)

\(\Leftrightarrow\frac{\left(-1\right)^3}{3^3}\times x=\frac{1}{3^4}\)

\(\Leftrightarrow x=\frac{1}{3^4}:\frac{-1}{3^3}\)

\(\Leftrightarrow x=\frac{1\times3^3}{3^4\times\left(-1\right)}\)

\(\Leftrightarrow x=\frac{1}{-3}\)

c)\(\Leftrightarrow\left(x-\frac{1}{2}\right)^3=\left(\frac{1}{3}\right)^3\)

\(\Leftrightarrow x-\frac{1}{2}=\frac{1}{3}\)

\(\Leftrightarrow x=\frac{1}{3}+\frac{1}{2}\)

\(\Leftrightarrow x=\frac{5}{6}\)

d)\(\Leftrightarrow\left(x+\frac{1}{2}\right)^4=\left(\frac{2}{3}\right)^4\)

\(\Leftrightarrow x+\frac{1}{2}=\frac{2}{3}\)

\(\Leftrightarrow x=\frac{2}{3}-\frac{1}{2}\)

\(\Leftrightarrow x=\frac{1}{6}\)

Đáp án B

Đáp án : B

a)= ( 81 , 6 x 27 , 3 – 17 , 3 x 81 , 6 ) x 0

=0 ( vì 0 nhân với số nào cũng bằng 0)

b)= ( 13 , 75 – 0 , 48 x 5 ) x ( 42 , 75 : 3 + 2 , 9 ) x ( 9-9)

= ( 13 , 75 – 0 , 48 x 5 ) x ( 42 , 75 : 3 + 2 , 9 ) x 0

= 0 ( vì 0 nhân với số nào cũng bằng 0)

c)=( 792 , 81 x 0 , 25 + 792 , 81 x 0 , 75 ) x 0

=0 ( vì 0 nhân với số nào cũng bằng 0 )

a ) ( 81 , 6 x 27 , 3 – 17 , 3 x 81 , 6 ) x ( 32 x 11 - 3200 x 0 , 1 - 32 )

= ( 81 , 6 x 27 , 3 – 17 , 3 x 81 , 6 ) x ( 352 - 320 - 32 )

= ( 81 , 6 x 27 , 3 – 17 , 3 x 81 , 6 ) x 0

= 0.

b ) ( 13 , 75 – 0 , 48 x 5 ) x ( 42 , 75 : 3 + 2 , 9 ) x ( 1 , 8 x 5 – 0 , 9 x 10 )

= ( 13 , 75 – 0 , 48 x 5 ) x ( 42 , 75 : 3 + 2 , 9 ) x ( 9 - 9 )

= ( 13 , 75 – 0 , 48 x 5 ) x ( 42 , 75 : 3 + 2 , 9 ) x 0

= 0

c ) ( 792 , 81 x 0 , 25 + 792 , 81 x 0 , 75 ) x ( 11 x 9 – 900 x 0 , 1 – 9 )

= ( 792 , 81 x 0 , 25 + 792 , 81 x 0 , 75 ) x ( 99 - 90 - 9 )

= ( 792 , 81 x 0 , 25 + 792 , 81 x 0 , 75 ) x 0

= 0.

Hok tốt !

a)32 x 11 -3200x 0,1 -32

=32x11-32x100x0,1-32

=32x(11-10-1)=32x0=0

nên(81,6x27,3-17,3x81,6)x(32x11-3200x0,1-32)

=(81,6x27,3-17,3x81,6)x0

=0

b)1,8x5 -0,9x10=1,8x5-0,9x2x5

=1,8x5-1,8x5

=0

nên (13,75-0,48 x 5)x(42,75:3+2,9)x(1,8x5-0,9x10)=0

c)(792,81x0,25+792,81x0,75)x(11x9-900x0,1-9)

=792,81x(0,25+0,75)x(99-90-9)

=792,81x1x0

=0

tu hoc moi gioi

xin lỗi mình viết nhầm cho gửi lại câu hỏi!

CHO \(A=\left(\left(\frac{x+7}{x+9}+\frac{x+7}{x^2+81-18x}+\frac{x+5}{x^2-81}\right)\left(\frac{x-9}{x+3}\right)^2\right)^{ }:\left(\frac{x+7}{x+3}\right)\)

a) Rút gọn A

b) Tìm số nguyên x để A nguyên

a, \(x=\dfrac{3}{4}-1=\dfrac{3}{4}-\dfrac{4}{4}=-\dfrac{1}{4}\)

b, \(x=\dfrac{1}{5}-4=\dfrac{1}{5}-\dfrac{20}{5}=-\dfrac{19}{5}\)

c, \(x=2+\dfrac{1}{5}=\dfrac{10}{5}+\dfrac{1}{5}=\dfrac{11}{5}\)

d, \(x=\dfrac{1}{81}-\dfrac{5}{3}=\dfrac{1}{81}-\dfrac{135}{81}=-\dfrac{134}{81}\)

\(a,\dfrac{3}{4}-x=1\\ \Rightarrow x=1,75\\ b,x+4=\dfrac{1}{5}\\ \Rightarrow x=-3,8\\ c,x-\dfrac{1}{5}=2\\ \Rightarrow x=2,2\\ d,x+\dfrac{5}{3}=\dfrac{1}{81}\\x=\dfrac{1}{81}-\dfrac{5}{3}\\ \Rightarrow x=-\dfrac{134}{81}\)

a) \(\dfrac{3}{4}-x=1\)

\(x=\dfrac{3}{4}-1\)

\(x=-\dfrac{1}{4}\)\(=0,25\)

b) \(x+4=\dfrac{1}{5}\)

\(x=\dfrac{1}{5}-4\)

\(x=-\dfrac{19}{5}\)\(=-3,8\)

c) \(x-\dfrac{1}{5}=2\)

\(x=2+\dfrac{1}{5}\)

\(x=\dfrac{11}{5}=2,2\)

d) \(x+\dfrac{5}{3}=\dfrac{1}{81}\)

\(x=\dfrac{1}{81}-\dfrac{5}{3}\)

\(x=-\dfrac{134}{81}\)

a. 96 : 8 : 2 = 6

96 : ( 8 x 2 ) = 6

96 : 8 : 2 = 96 : ( 8 x 2 )

b. 81 : 9 : 3 = 3

81 : ( 9 x 3 ) = 3

81 : 9 : 3 = 81 : ( 9x 3)

a) \(3^{a+1}=81\)

\(3^{a+1}=3^4\)

\(a+1=4\)

\(a=3\)

b) \(\left(x-1\right)^3=27\)

\(\left(x-1\right)^3=3^3\)

\(x-1=3\)

\(x=4\)

\(a,3^{a+1}=81\\ \Rightarrow3^{a+1}=3^4\\ \\ \Rightarrow a+1=4\\ \Rightarrow a=3.\\ b,\left(x-1\right)^3=27\\ \Rightarrow\left(x-1\right)^3=3^3\\ \Rightarrow x-1=3\\ \Rightarrow x=4.\)