Write $(5-5 i)^2$ in the form $a+b i$, where $a$ and $b$ are real numbers.
The problem asks to expand the expression \((5-5i)^2\) and express it in the standard form of a complex number, \(a+bi\), where \(a\) and \(b\) are real numbers and \(i\) is the imaginary unit defined by \(i^2 = -1\). This is an exercise in applying algebraic binomial expansion to complex numbers.
To expand the squared binomial \((5-5i)^2\), we use the algebraic identity \((x-y)^2 = x^2 - 2xy + y^2\). Here, let \(x = 5\) and \(y = 5i\). Substituting these values into the identity, we get:
\[(5-5i)^2 = 5^2 - 2(5)(5i) + (5i)^2\]
Now, we calculate each term individually:
Combining these, we have:
\[(5-5i)^2 = 25 - 50i - 25\]
Subtracting the constant terms, we find:
\[(5-5i)^2 = -50i\]
This can be written in the form \(a+bi\) as \(0-50i\).
The final result of the expansion is \(-50i\). In the standard complex form \(a+bi\), we have \(a = 0\) and \(b = -50\). Thus, \((5-5i)^2 = \boxed{0-50i}\).
Complex number multiplication and exponentiation are essential in fields like electrical engineering and physics, particularly when analyzing alternating current (AC) circuits or wave phenomena. For example, when calculating the impedance of a circuit, engineers use complex numbers to represent both resistance and reactance, allowing them to simplify complex oscillating systems into manageable algebraic equations. Mastering this allows you to solve problems involving phase shifts and signal propagation with ease.