Draw a geometric figure so that its area can represent (a + 3b) (a-b)

Draw a geometric figure so that its area can represent (a + 3b) (a-b)

Draw a ray ox, intercept OA = a, Aa1 = B, A1A2 = B, A2B = B on this line, then AB = 3b, OB = a + 3B,
Let's make the perpendicular POY of ox, the perpendicular foot is O, intercept OC = a on oy, and then take point C as the starting point, intercept CD on CO as B, then od = A-B, make DF parallel to ob and equal to ob, connect BF, then the area of rectangular obfd is (a + 3b) (a-b)

Use geometric figure to explain: the square of a + AB + AC = a (a + B + C)

Make a rectangle with length a + B + C and width a
In this case, rectangle area = a (a + B + C)
Divide the length of the rectangle into a, B and C, and make the height at the dividing point,
Then the area of rectangle = the sum of the areas of three rectangular quadrilaterals = a ^ 2 + AB + AC
So a ^ 2 + AB + AC = a (a + B + C)