If a = 4, then you would plug in the value of a for the variable in the formula and solve by following the order of operations.
a^2 - 7a + 3 would be 4^2 - 7(4) + 3 if a = 4.
First, solve exponents.
4^2 = 16
16 - 7(4) + 3
Then, multiply.
7 • 4 = 28
16 - 24 + 3
Lastly, subtract and add in order of left to right.
16 - 24 = -8
-8 + 3 = -5
So the answer to this expression is -5 when a = 4.
Answer:
-5
Hope this helps!