Question

What is the value of `n` such that `x^2 - 10x + n` is a perfect square trinomial?

Answer 1

`25`

Explanation:

`(x-5)^2 = x^2-2x(5)+5^2 = x^2-10x+25`

In general:

`(a+b)^2 = a^2+2ab+b^2`

In our example, `a=x`, `b=-5`

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Or if you prefer, you can write:

`(a-b)^2 = a^2-2ab+b^2`

with `a=x` and `b=5`