The equation a = StartFraction one-half EndFraction left-parenthesis b 1 plus b 1 right-parenthesis.(b1 + b2)h can be used to determine the area, a, of a trapezoid with height, h, and base lengths, b1 and b2. Which are equivalent equations? Check all that apply. StartFraction 2 a Over h EndFraction minus b 2 equals b 1.– b2 = b1
StartFraction a Over 2 h EndFraction minus b 2 equals b 1. – b2 = b1
StartFraction 2 a minus b 2 Over h EndFraction equals b. = b1
StartFraction 2 a Over b 1 plus b 2 EndFraction equals h. = h
StartFraction a Over 2 left-parenthesis b 1 plus b 1 right-parenthesis EndFraction equals h.= h

Can anyone explain HOW they got the answers A and D??