8x : 2x = 4
<=> (8 : 2)x = 4
<=> 4x = 4
<=> x = 1
S = 22 + 42 + 62 + ... + 202
S = (22 + 42 + 62 + ... + 202)
S =22.(12 + 22 + 32 + ... + 102 )
S = 4. 385 = 1540
/Tìm X biết
\(8^x:2^x=4\)
\(\Leftrightarrow\left(8:2\right)^x=4\)
\(\Rightarrow4^x=4^1\)
\(\Rightarrow x=1\)
\(s=2^2+4^2+6^2+...+20^2\)
\(\Rightarrow s=2^2.\left(1^2+2^2+3^2+...+10^2\right)\)
\(\Rightarrow s=4.385=1540\)
*Hok tốt *
Ta Có :\(8^x:2^x=(8:2)^x\)
\(\Rightarrow(8:2)^x=4\)
mà \((8:2^{ })^x=4^x\)