Final answer:
The zero of the equation y = -7x - 21 is the value of x when y equals zero, which is x = -3.
Step-by-step explanation:
The zero of the equation y = -7x - 21 is the value of x when y equals zero. To find this, we set y to zero and solve for x:
0 = -7x - 21
Add 21 to both sides:
21 = -7x
Divide both sides by -7:
x = -3
So, the zero of the equation is x = -3.