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This is Josh’s solution for the equation x^2-6x-7=0
x^2-6x-7=0
x^2-6x=7
x^2-6x+9=7+9
(x-3)^2=16
x-3=16
x=19
x-3=-16
x=-13

explain what mistake he made on step 5 which is x-3=16

Respuesta :

fieryanswererft

Answer:

  • See below.

Explanation:

easy way to solve:

[tex]x^2-6x-7=0[/tex]

[tex]x^2+x-7x-7=0[/tex]

[tex]x(x+1)-7(x+1) =0[/tex]

[tex](x-7)(x+1)= 0[/tex]

[tex]x = 7, -1[/tex]

Mistake:

In step 5,

Josh should have given:

[tex](x-3)^2=16[/tex]

[tex]x-3 = \pm \sqrt{16}[/tex]     [ changing sides changes square sign to [tex]\pm[/tex] square root ]

[tex]x-3 = \pm 4[/tex]

[tex]x -3 = 4[/tex], [tex]x-3 = -4[/tex]

[tex]x = 7[/tex], [tex]x = -1[/tex]

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