B1:

Ta có: \(\frac{4^6.9^5+6^9.120}{8^4.3^{12}-6^{11}}=\frac{2^{12}.3^{10}-2^9.3^9.2^3.3.5}{2^{12}.3^{12}-2^{11}.3^{11}}\)

\(=\frac{2^{12}.3^{10}-2^{12}.3^{10}.5}{2^{12}.3^{12}-2^{11}.3^{11}}=\frac{2^{12}.3^{10}.\left(1-5\right)}{2^{11}.3^{11}.\left(2.3-1\right)}\)

\(=\frac{2.\left(-4\right)}{3.5}=-\frac{8}{15}\)

B2:

Ta có: \(1+3+5+...+x=1600\)

\(\Leftrightarrow\frac{\left(x+1\right)\cdot\left(\frac{x-1}{2}+1\right)}{2}=1600\)

\(\Leftrightarrow\left(x+1\right)\cdot\frac{x+1}{2}=3200\)

\(\Leftrightarrow\left(x+1\right)^2=6400\)

Xét theo dãy tăng tiến ta thấy được giá trị của x càng tăng

=> x dương => x + 1 dương

\(\Rightarrow x+1=80\)

\(\Rightarrow x=79\)

   325-5*[4³-(27-5²):1¹⁸]

= 325-5*[64-(27-25):1]

= 325-5*[64-2:1]

=325-5*62

=352-310

=42

\(a)x^{15}=x\)

\(\Rightarrow x^{15}-x=0\)

\(\Leftrightarrow x\left(x^{14}-1\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x=0\\x^{14}-1=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=0\\x=1\end{cases}}}\)

Vậy....

\(b)2^x-15=17\)

\(\Leftrightarrow2^x=32\)

\(\Leftrightarrow2^x=2^5\)

\(\Rightarrow x=5\)

Vậy...

\(c)\left(2x+1\right)^3=125\)

\(\Leftrightarrow\left(2x+1\right)^3=5^3\)

\(\Rightarrow2x+1=5\)

\(\Leftrightarrow2x=4\Rightarrow x=2\)

Vậy...

_Y nguyệt_

\(a)x^{15}=x\)

\(\Rightarrow x=1\)

\(b)2^x-15=17\)

\(\Rightarrow2^x=32\)

\(\Rightarrow2^x=2^5\Rightarrow x=5\)

\(c)\left(2x+1\right)^3=125\)

\(\Rightarrow2x+1=5\)

\(\Rightarrow x=2\)

\(=5^2\left(\frac{5}{8.13}+\frac{5}{13.18}+...+\frac{5}{93.98}\right).\frac{392}{17}\)

\(=5^2\left(\frac{1}{8}-\frac{1}{13}+\frac{1}{13}-\frac{1}{18}+...+\frac{1}{93}-\frac{1}{98}\right)\frac{392}{17}\)

\(=25\left(\frac{1}{8}-\frac{1}{98}\right)\frac{392}{17}\)

\(=25\times\frac{45}{392}\times\frac{392}{17}\)

\(=25\times\frac{45}{17}\)

\(=\frac{1125}{17}\)

\(5^2.\left(\frac{5}{8.13}+\frac{5}{13.18}+\frac{5}{18.23}+...+\frac{5}{93.98}\right).\frac{392}{5^2}\)

\(\left(\frac{1}{8}-\frac{1}{13}+\frac{1}{13}-\frac{1}{18}+...+\frac{1}{93}-\frac{1}{98}\right).392=\left(\frac{1}{8}-\frac{1}{98}\right).392=45\)

a) \(5^x=5^3\)

b)\(3^{2x}=3^{2.2}\)

c)\(5^{2x-3}=5^{2.3-3}\)

THỈNH THOẢNG CŨNG CO 1 MỐNG CHỨ NHỈ...

~ HỌC TỐT ~

a, 5 mũ 3 =125

b,3 mũ 2.2 =81

c,x = 1