1. **Stating the problem:** Simplify the expression $$(2a+b)\cdot(2a+b)+4$$ 2. **Formula and rules:** Use the distributive property (FOIL) to expand the product of binomials: $$(x+y)(x+y) = x^2 + 2xy + y^2$$ 3. **Intermediate work:** $$ (2a+b)(2a+b) + 4 = (2a)^2 + 2 \cdot 2a \cdot b + b^2 + 4 $$ $$ = 4a^2 + 4ab + b^2 + 4 $$ 4. **Final answer:** $$ 4a^2 + 4ab + b^2 + 4 $$