Toán Lớp 9: tính chính xác 20072008 × 20202021

Question

Toán Lớp 9:  tính chính xác  20072008 × 20202021

minhtuyethue · Answer

20072008 &times; 20202021=405495127128168=4.054951271x10^14

quynhmaithu · Answer

Giải đáp:    $ displaystyle  begin{array}{{>{ displaystyle}l}} 20072008   times   20202021  =405495127128168    end{array}$     Giải th&iacute;ch đ&aacute;p &aacute;n:     $ displaystyle  begin{array}{{>{ displaystyle}l}} Đặt  A=20072008.20202021   Ta  c&oacute;:   20072008=20000000+70000+2000+8   20202021=20000000+200000+2000+20+1   Đặt  20000000=a;70000=b;2000=c;8=d,200000=e;20=f     v&agrave;  1=g    Rightarrow A=( 20000000+70000+2000+8) .   ( 20000000+200000+2000+20+1)   =a^{2} +ae+ac+af+ag  +  ba+be+bc+bf+bg     +  ca+ce+c^{2} +cf+cg  +  da+de+dc+df+dg   =4.10^{14} +4.10^{12} +4.10^{10} +4.10^{8} +0,2.10^{6}      +1,4.10^{12} +1,4.10^{10} +1,4.10^{8} +1,4.10^{6} +7.10^{4}   +  4.10^{10} +4.10^{8} +4.10^{6} +4.10^{4} +0,2.10^{4}   +1,6.10^{8} +1,6.10^{6} +1,6.10^{4} +1,6.10^{2} +8   =4.10^{14} +5,4.10^{12} +9,4.10^{10} +11.10^{8} +7,2.10^{6} +12,8.10^{4} +1,6.10^{2} +8   =405495127128168  end{array}$