Multiplying polynomials with an area model

MathematicsAlgebraAges 13–14

A rectangle with length a + b and width c + d is split into 4 cells. Students drag the handles on the edges to change a, b, c, d and see that each cell is a product (a monomial), with the sum of the four cells equal to (a + b)(c + d). Switch to (x + b)(x + d) mode to see x² + (b + d)x + bd.