How do you solve using the completing the square method #x^2+10x-4=0#?

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Answer 1 · 2016-08-01T10:37:14

#x=+-sqrt29-5#

You can express your quadratic equation as:
#x^2+10x-4=(x+a)^2+b#

#(x+a)^2+b=x^2+2ax+a^2+b#

You will find #2ax=10x# hence #a=5#
#a^2+b=-4#
#5^2+b=-4#
#b=-29#

Now you have: #(x+5)^2-29=0#
#(x+5)^2=29#
#(x+5)=+-sqrt29#
#thereforex=+-sqrt29-5#

Answer 2 · 2016-08-01T10:43:15

#x= -5+-sqrt29#

#x^2+10x-4=0 or (x+5)^2 -25-4=0 or (x+5)^2=29 or (x+5)=+-sqrt29 or x= -5+-sqrt29#[Ans]