让DE = x时,则AE = 4 + X
三角形ABE = S为S梯形ABDF + S三角形DEF = 4×(4 + X)÷2(1)
S梯形正方形ABCD = S ABDF + S三角形BCF = 4×4(2)
(1) - (2),
三角三角形DEF-S BCF = 4×(4 + X)÷2-4× 4 = 6
解决,4 + X = 11
X = 7
所以DE是7厘米长.
让DE = x时,则AE = 4 + X
三角形ABE = S为S梯形ABDF + S三角形DEF = 4×(4 + X)÷2(1)
S梯形正方形ABCD = S ABDF + S三角形BCF = 4×4(2)
(1) - (2),
三角三角形DEF-S BCF = 4×(4 + X)÷2-4× 4 = 6
解决,4 + X = 11
X = 7
所以DE是7厘米长.