Question 100957
x^2 + 15 = -10x
x^2+10x+15=0 make equation = 0
x^2+10x=-15 put the constant on the right side.
x^2+10x+25=-15+25 divide the coefficient of x in half and square it to get the new constant and add it to both sides.
(x+5)^2=10 factor the left side.
x+5=+-sqrt(10) get sqrt of both sides.
x= -5+sqrt(10), -5-sqrt(10) 
Ed