答:
如图:
S阴影=矩形面积-S1-S2-S3-S4-S5-S6
=6b·7a-(3b·5a)/2-3b·5a-(3b·2a)/2-(4b·a)/2-(6a·2b)/2-2b·a
=42ab-15ab/2-15ab-3ab-2ab-6ab-2ab
=13ab/2
答:
如图:
S阴影=矩形面积-S1-S2-S3-S4-S5-S6
=6b·7a-(3b·5a)/2-3b·5a-(3b·2a)/2-(4b·a)/2-(6a·2b)/2-2b·a
=42ab-15ab/2-15ab-3ab-2ab-6ab-2ab
=13ab/2