If $$(2.1× 2.1)-(2×a×2.1)+ (0.6×0.6)={(1.5)}^2$$​, then find the value of a.

Correct option is A

​Given:

​$$(2.1 \times 2.1) - (2 \times a \times 2.1) + (0.6 \times 0.6) = 1.5^2$$​​

Solution:

$$2.1 \times 2.1 = 4.41, \quad 2 \times a \times 2.1 = 4.2a, \quad 0.6 \times 0.6 = 0.36, \quad 1.5^2 = 2.25$$ 

Now, expression becomes

​$$4.41 - 4.2a + 0.36 = 2.25 \\ \ \\ 4.77−4.2a=2.25 \\ \ \\ -4.2a = 2.25 - 4.77 = -2.52 \\ \ \\ a = \frac{-2.52}{-4.2} = 0.6$$​​