Blissviz
Answered

Solving QE by Completing Square: Solve and check.

x^2 + 4x - 21 = 0

Sagot :

OhHarryviz
answer: (x-3)(x+7)=0
check:
(x-3)(x+7)=0
x^2+7x-3x-21=0
x^2+4-21=0
AnneCviz
[tex] x^{2} +4x-21=0[/tex]

[tex] x^{2} +4x=21[/tex]

[tex] x^{2} +4x+4=21+4[/tex]

[tex](x+2)^2=25[/tex]

[tex](x+2)=\pm \sqrt{25} =\pm5[/tex]

[tex]x=\pm5-2[/tex]

[tex]x_1=5-2=\boxed{3}[/tex]

[tex]x_2=-5-2=\boxed{-7}[/tex]

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