A square is made from tiles representing x²+8x+16. What will be its side?

Correct answer: x+4

The correct answer is B: x+4. We look for a perfect-square expression. The constant 16 is 4², so the small corner tile has side 4. The expression x²+8x+16 matches the identity x²+2·x·4+4²=(x+4)². In the tile model, there is one x² tile, two x-by-4 rectangular tiles whose combined area is 8x, and one 4-by-4 tile with area 16. Therefore the complete square has side x+4. Option A would produce x²+16x+64, not the given expression. Option C gives incorrect cross and constant terms. Option D would produce a negative middle term, x²-8x+16. Memory cue: take the square root of the constant, then check that twice its product with x equals the middle coefficient.