Réponse:
To express the given complex number in the form a+ib, we need to simplify the expression.
First, let's simplify the real part:
(8-21) = -13
Now, let's simplify the imaginary part:
-(1+7i) = -1 - 7i
Putting it all together, the complex number (8-21)-(1+7i) can be expressed in the form a+ib as:
-13 - (1 + 7i)
Therefore, the expression in the desired form is:
-13 - 1 - 7i = -14 - 7i
