How do you solve #-x ^ { 2} + 13x + 39= - 2x ^ { 2} - 3#?

1 Answer
Austte
Oct 15, 2017

#x_1=-7#
#x_2=-6#

Explanation:

Move expression to the left
#-x^2+13x+39+2x^2+3=0#
Collect the like terms and calculate the sum
#x^2+13x+42=0#
Solve the quadratic equation #ax^2+bx+c=0# by discriminant formula: #D=b^2-4ac#
#D=13^2-4×1×42=1#
#x_1=\frac {-b-sqrtD}{2a}#

#x_2=\frac {-b+sqrtD}{2a}#

#x_1=\frac {-13-1}{2}=-7#

#x_2=\frac {-13+1}{2}=-6#

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