Question 418948
subtracting 20 ___ x^2 + 9x = -20


when the coefficient of the squared term is one (as in this case)
___ take half of the 1st order coefficient , square the quantity , add to both sides of equation


x^2 + 9x + (9/2)^2 = -20 + (9/2)^2


[x + (9/2)]^2 = -(80/4) + (81/4)


x + (9/2) = sqrt(1/4)


x = -(9/2) ± (1/2)


x = -5 ___ and ___ x = -4