To find the area of a rhombus, multiply the lengths of the two diagonals and divide by 2 (same as multiplying by 1/2): The sides and angles of a rhombus: The sides of a rhombus are all congruent (the same length.) Opposite angles of a rhombus are congruent (the same size and measure.)
A square has two perpendicular bisectors but a square is not a rhombus (because a rhombus does not have all four angles = 90. Oh, but wait, a rhombus is a square in the same way a rectangle is a square but not the other way around.
 
        
             
        
        
        
Answer:
11.8
Step-by-step explanation:
3(12.4) + 6(11.5) =  37.2 + 69 = 106.2
106.2/9 = 11.8
 
        
             
        
        
        
Answer:
y=-3x-3
Step-by-step explanation:
9x+3y=-9
This is currently in standard form, or ax+by=c.
To get it to slope-intercept form, (y=mx+b) first subtract 9x to both sides.
3y=-9x-9
Divide both sides by 3.
y=-3x-3