Which formula is incorrect for calculating the area of a trapezoid?

The area of a trapezoid is typically calculated using the formula A = (1/2)h(b1 + b2), where h represents the height of the trapezoid and b1 and b2 represent the lengths of the two parallel bases. This formula emphasizes that the area is a function of the average of the lengths of the bases, multiplied by the height.

When examining the other provided formula, which suggests A = (1/2)(b1 - b2)h, it diverges from the established method for area calculation. The subtraction of the base lengths instead of adding them does not accurately reflect the geometry of a trapezoid since we need to consider the total horizontal distance spanned by both bases, not the difference between their lengths.

Hence, the only correct formula is A = (1/2)h(b1 + b2), and similarly, A = (1/3)(b1 + b2)h is incorrect as it improperly modifies the standard area formula for a trapezoid by introducing an incorrect constant of proportionality. This maintains the emphasis on adding the bases together rather than using a difference or an incorrect multiplier. Therefore, it confirms that the area of a trapezoid cannot be