Answer:
B. 25
Step-by-step explanation:
[tex](a+b)^2=a^2+2ab+b^2\\\\\text{We have}\\\\x^2+10x=0\\\\x^2+2(x)(5)=0\\\\\text{Therefore we have}\ a=x\ \text{and}\ b=5.\\\\\text{We need}\ b^2\to5^2.\\\\x^2+2(x)(5)=0\qquad\text{add}\ 5^2\ \text{to both sides}\\\\x^2+2(x)(5)+5^2=5^2\\\\(x+5)^2=25[/tex]
