In a visual model, the rectangular form of (c²-d²) is equal to what?

Correct answer: (c+d)(c-d)

Direct answer: D, (c+d)(c-d). Begin with a large square of side c, whose area is c². Remove a smaller square of side d, whose area is d². The remaining region has area c²-d². If this remaining region is rearranged into a rectangle, its two dimensions are c+d and c-d. Therefore, c²-d²=(c+d)(c-d), the difference-of-squares identity. A gives only c(c-d), which does not include the complete factor c+d. B has the wrong factors and represents a different product. C uses addition rather than subtraction, so it is the sum of two squares, not the remaining area. D is correct because multiplying it gives c²-cd+cd-d²=c²-d². Cue: difference of squares means sum of terms times their difference.