How much is the root sign (2's square + X's Square) equal to

How much is the root sign (2's square + X's Square) equal to

I can't drive it out
Or is it equal to
Under the root sign (square of 2 + square of x)

Urgent! The square of X in junior high school plus 5x minus 125 equals 0, when x = 1, x = 2
Brother, how do you always calculate? Give me a process

Substituting x = 1 into the original formula, we get 1 + 5-125 = - 119
Substituting x = 2 into the original formula, we get 4 + 10-125 = - 111
So when x = 1, the original formula = - 119
When x = 2, the original formula = - 111

The square of the sum of a number and 8 is 15 times its sum minus 5

Let this number be X
Then (x + 8) & sup2; = 15x-5
x²+16x+64=15x-5
x²+x+69=0
x²+x+1/4=1/4-69
(x+1/2)²=-275/4
The result is complex: x = - 1 / 2 ± √ 275 / 2
I don't know if you gave me the wrong terms

I just asked wrong! The square of halo x plus 5x minus 125 equals 0, when x = 1, x = 2
How to decompose the square of x plus 5x minus 125 equal to 0

Inseparable with the formula to do
X = - B + or - followed by B ^ 2-4ac / 2A
[x - (- 5 + 5 follow 21) / 2] [x - (- 5-5 follow 21) / 2]