Which expression is a perfect-square trinomial and can be factorised using \(a^2+2ab+b^2=(a+b)^2\)?

Correct answer: \(x^2+10x+25\)

Direct answer: A, \(x^2+10x+25=(x+5)^2\). Compare the expression with \(u^2+2uv+v^2\). Here the first square is \(x^2\, so u=x\), and the last term 25 is \(5^2\), so v=5. The required middle term is then \(2uv=2(x)(5)=10x\), exactly as given. Thus A is a perfect-square trinomial. Option B fails because with first and last terms x² and 25, the middle term must be 10x, but its constant is 20. Option C is also a perfect square, \((x-5)^2\), but it has a negative middle term and therefore does not match the specifically stated plus identity. Option D has only two terms, not a trinomial. Memory cue: square the first and last roots, then check whether the middle term is twice their product.