Final answer:
To find a number a such that the tangent lines to y = x + 7x² + x + 12 at x = a and at x = a + 1 are parallel, we need to find the slope of the tangent lines at these points. However, there is no number a that satisfies this condition.
Step-by-step explanation:
To find a number a such that the tangent lines to y = x + 7x² + x + 12 at x = a and at x = a + 1 are parallel, we need to find the slope of the tangent lines at these points. The slope of a tangent line to a function is given by the derivative of the function evaluated at the specific x-value. So, we need to find the derivative of y = x + 7x² + x + 12 and set it equal to the same value for x = a and x = a + 1. Let's find the derivative first:
y' = 1 + 14x + 1 = 14x + 2
Now, we set the derivative equal to the same value:
14a + 2 = 14(a + 1) + 2
14a + 2 = 14a + 14 + 2
14a + 2 = 14a + 16
Subtracting 14a from both sides:
2 = 16
This equation is not true for any value of a. Therefore, there is no number a such that the tangent lines to y = x + 7x² + x + 12 at x = a and at x = a + 1 are parallel.