SOLUTION: Hi, I need some help with this function... f(a+3)=2x^2+2x-3 I know how to find this much of the answer 2a^2+?+21. I am not sure how to find the middle number. Please show y

Algebra ->  Functions -> SOLUTION: Hi, I need some help with this function... f(a+3)=2x^2+2x-3 I know how to find this much of the answer 2a^2+?+21. I am not sure how to find the middle number. Please show y      Log On


   

Question 988261: Hi,
I need some help with this function...
f(a+3)=2x^2+2x-3
I know how to find this much of the answer 2a^2+?+21. I am not sure how to find the middle number. Please show your work so I can figure out how to do it!
Thank you!
Answer by vleith(2983) About Me  (Show Source):
You can put this solution on YOUR website!
substitute (a+3) for x everywhere , then simply
f%28a%2B3%29=+2%2A%28a%2B3%29%5E2++%2B+2%2A%28a%2B3%29+-3+
f%28a%2B3%29=+2%2A%28a%5E2+%2B6a+%2B9%29++%2B+2a%2B6+-3+
f%28a%2B3%29=+2a%5E2+%2B12a+%2B18++%2B+2a%2B6+-3+
f%28a%2B3%29=+2a%5E2+%2B14a+%2B21