Express the complex number given below in the form $a+ib$: $(5i)\;(-\large\frac{3}{5}$$i) 1 Answer Toolbox: • A number of the form a + ib, where a and b are real numbers, is called a complex number, a is called the real part and b is called the imaginary part of the complex number. Given: (5i)\;(-\large\frac{3}{5}$$i)$
$\Rightarrow (5i)\;(-\large\frac{3}{5}$$i) = -5 \times \large\frac{3}{5}$$ \times i \times i = -3 i^2$
$\qquad \qquad = -3 (-1) = 3 \quad (\because i^2 = -1)$