(7а*b)2 =

To simplify the expression \((7a \cdot b)^2\), you can apply the power of a product property, which states that \((xy)^n = x^n \cdot y^n\).

Here's the step-by-step simplification:

\[ (7a \cdot b)^2 = (7a)^2 \cdot (b)^2 \]

Now, calculate \((7a)^2\):

\[ (7a)^2 = 7^2 \cdot a^2 = 49a^2 \]

So, the expression becomes:

\[ (7a \cdot b)^2 = 49a^2 \cdot b^2 \]

Thus, the final result is:

\[ (7a \cdot b)^2 = 49a^2b^2 \]