Need Help Checking My Answer

Find the term that must be added to the expression to create a perfect sqaure trinomial. x^2 + 22x

Okay...I got (x + 11)2 = 121 So x = -22 is my final answer. Is this correct???????????? :roll:

(x+11)<SUP>2</SUP>=x<SUP>2</SUP>+22x+121.

ProfessorFilostrato said:

Find the term that must be added to the expression to create a perfect sqaure trinomial. x^2 + 22x

Click to expand...

22/2 = 11

11² = 121

It seems to me the actual answer to the actual question is 121.

Hello, ProfessorFilostrato!

Find the term that must be added to the expression to create a perfect square trinomial: x² + 22x

Click to expand...

Evidently, you've never heard of "completing the square".

We are given the first two terms of a square trinomial and we must find the third (constant) term.

Rule: Take one-half of the x-coefficient . . . and square.

. . . Half of 22 = 11 . . . then 11² = 121

. . . Therefore, 121 must be added.


<u>Check</u>: . x² + 22x + 121 . = . (x + 11)(x + 11) . = . (x + 11)² . . . yes!