Answer:
x = -5 plus/minus sqrt( 26 )
Step-by-step explanation:
Let's remember the binomial square formula
A^2 + 2AB + B^2 = (A + B)^2
We have:
x^2 + 2*5x -1
Hence, if we replace
A = x
B = 5
we get a perfect square: x^2 + 2*5x + 25 = (x + 5)^2. [++]
Based on this reasoning, let's set f(x) = 0
x^2 +10x -1 = 0
Let's add 26 on both terms:
x^2 +10x +25 = 26
Based on [++]: (x + 5)^2 = 26
Square root on both sides
(x + 5) = plus/minus sqrt (26)
x = -5 plus/minus sqrt (26)
