How do i find equation of the line of symmetry?

The axis of symmetry is also defined by the following equation:

x = -b/2a

Always keep in mind that a quadratic function has the following form:

y = ax2 + bx + c

Follow 4 steps to use an equation to calculate the line of symmetry for y = x2 + 2x

-Identify a and b for y

-Plug into the equation x = -b/2a

-Simplify

-You have your line of symmetry.

Hope this helps!

a_n = a_1 + (n - 1)d

the first term is 6.

the common difference d = ?

when you find d, replace n with 7 and d with the common difference to find your answer.