My homework is telling me that the square root of x^2+(x^2-10)^2 is equal to the square root of x^4-19x^2+100 .... I don't understand where the -19x^2 comes from
x^2+(x^2-10)^2 → x^2 + x^4 -2*10*x^2 + 10^2 → x^2 + x^4 -20x^2 + 100 → x^4 + (1 - 20)x^2 + 100 → x^4 - 19x^2 + 100
