Dien h ban dau la:
\(\frac{\left(6+4,8\right)\times5}{2}=27\left(dm^2\right)\)
Day be sau khi tang la:
\(1,2+4,8=6\left(dm\right)\)
Day lon sau khi tang la:
\(2,5+6=8,5\left(dm\right)\)
Dien h hinh thang luc sau la:
\(\frac{\left(8,5+6\right)\times5}{2}=36,25\left(dm^2\right)\)
Dien h tang them:
\(36,25-27=9,25\left(dm^2\right)\)
D/s:
HTDT