Final answer:
To express (x+10)² as a trinomial in standard form, we need to expand the expression by squaring the binomial. The correct trinomial in standard form is x² + 20x + 100.
Step-by-step explanation:
To express (x+10)² as a trinomial in standard form, we need to expand the expression by squaring the binomial.
(x+10)² = x² + 2(10)(x) + (10)²
= x² + 20x + 100
Therefore, the correct trinomial in standard form is x² + 20x + 100 (option A).