có:a/b=b/c=c/d=>a^3/b^3=b^3/c^3=c^3/d^3

áp dụng tc dãy tỉ số = nhau 

a^3/b^=b^3/c^3=c^3/d^3=a^3+b^3+c^3/b^3+c^3+d^3 <()

ta có a/b=b/c=>a/b.b/c.c/d=b/c.b/c.c/d

=>a/d=b/c.b/c.b/c(b/c=c/d)

=>a/d=b^3/c^3 (2)

từ 1 và 2 suy ra

vậy..........

A+B=4x²-5x+1/2-4x²+2x-3/2=-3x-1

A-B=4x²-5x+1/2+4x²-2x+3/2=8x²-7x+2

\(\frac{7}{23}.\left(-\frac{8}{6}\right)-\frac{45}{18}=-\frac{28}{69}-\frac{45}{18}\)

                                    \(=-\frac{168}{414}-\frac{1035}{414}\)

                                    \(=-\frac{1203}{414}=-\frac{401}{138}\)

Ta có:\(\frac{x-100}{24}+\frac{x-98}{26}+\frac{x-96}{28}=3\)

\(\Rightarrow\)\(\frac{91x-100.91}{91.24}+\frac{84x-84.98}{26.84}+\frac{78x-96.78}{78.28}\)

=\(\frac{91x-9100+84x-8232+78x-7488}{2184}\)

=\(\frac{91x+84x+78x-9100-8232-7488}{2184}\)

=\(\frac{x\left(91+84+78\right)-\left(9100+8232+7488\right)}{2184}\)

=\(\frac{x253-24820}{2184}=3\)

\(\Rightarrow\)x253- 24820 =6552

\(\Rightarrow\)x253= 31372

\(\Rightarrow\)x = 124

\(\frac{x-100}{24}+\frac{x-98}{+26}+\frac{x-96}{28}=3\)

\(=\frac{\left(x-100\right)}{24}+\frac{\left(x-98\right)}{26}+\frac{\left(x-96\right)}{28}-1=0\)

\(\Leftrightarrow\frac{\left(x-100\right)}{24-1}+\frac{\left(x-98\right)}{26-1}+\frac{\left(x-96\right)}{28-1}=0\)

\(\Leftrightarrow\left(x-124\right)\left(\frac{1}{24}+\frac{1}{26}+\frac{1}{28}\right)=0\)

Vì: \(\frac{1}{24}+\frac{1}{26}+\frac{1}{28}\ne0\)

\(\Rightarrow x-124=0\)

\(\Rightarrow x=124-0\)

\(\Rightarrow x=124\)

ai ko bt = -3 giải rõ ràng đi              

\(2^{x-1}+5.2^{x-2}=\frac{7}{32}\)

\(2.2^{x-1}+5.2^{x-2}=\frac{7}{32}\)

      \(2^{x-2}.\left(5+2\right)=\frac{7}{32}\)

                   \(2^{x-2}.7=\frac{7}{32}\)

                       \(2^{x-2}=\frac{7}{32}:7\)

                       \(2^{x-2}=\frac{1}{32}\)

               \(\Rightarrow x-2=-5\)

                              \(x=-5+2\)

Vậy                           \(x=-3\)

-49/50                                  

Cách 1:

\(\left(6-\frac{2}{3}+\frac{1}{2}\right)-\left(5+\frac{5}{3}-\frac{3}{2}\right)-\left(3-\frac{7}{3}+\frac{5}{2}\right)\)

\(=\left(\frac{36-4+3}{6}\right)-\left(\frac{30+10-9}{6}\right)-\left(\frac{18-14+15}{6}\right)\)

\(=\frac{35}{6}-\frac{31}{6}-\frac{19}{6}\)

\(=\frac{35-31-19}{6}\)

\(=\frac{-15}{6}=\frac{-5}{2}\)

Cách 2:

\(\left(6-\frac{2}{3}+\frac{1}{2}\right)-\left(5+\frac{5}{3}-\frac{3}{2}\right)-\left(3-\frac{7}{3}+\frac{5}{2}\right)\)

\(=6-\frac{2}{3}+\frac{1}{2}-5-\frac{5}{3}+\frac{3}{2}-3+\frac{7}{3}-\frac{5}{2}\)

\(=6-5-3+\frac{1}{2}+\frac{3}{2}-\frac{5}{2}-\frac{2}{3}-\frac{5}{3}+\frac{7}{3}\)

\(=-2-\frac{1}{2}+0\)

\(=\frac{-5}{2}\)

= \(6-\frac{2}{3}+\frac{1}{2}-5-\frac{5}{3}+\frac{3}{2}-3+\frac{7}{3}-\frac{5}{2}\)

\(=\left(-\frac{2}{3}-\frac{5}{3}+\frac{7}{3}\right)+\left(\frac{1}{2}+\frac{3}{2}-\frac{5}{2}\right)+\left(6-5-3\right)=0-\frac{1}{2}-2=-\frac{5}{2}\)