# How do you find the missing number or term to make a perfect square trinomial. y^2 + 0.1y +___?

Jul 5, 2015

I found: ${y}^{2} + 0.1 y + {\left(0.05\right)}^{2} = {y}^{2} + 0.1 y + 0.0025$

#### Explanation:

I would write it as:
${y}^{2} + \frac{1}{10} y + \ldots .$
the missng number must be such that multiplied by $2$ gives $\frac{1}{10}$;
it could be $\frac{1}{20}$; so the complete trinomial could be:
${y}^{2} + \frac{1}{10} y + \frac{1}{20} ^ 2 = {\left(y + \frac{1}{20}\right)}^{2}$
in decimal form:
${y}^{2} + 0.1 y + {\left(0.05\right)}^{2} = {y}^{2} + 0.1 y + 0.0025$