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# x 2 +3x−8=80

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x 2 +3x−8=80

Guest Mar 31, 2015

#1
+91510
+5

\$\$\\x^ 2 +3x-8=80\\\\
x^ 2 +3x-88=0\\\\\$\$

now I need two numbers that multiply to -88

(forgetting about the minius sign it could be    8*11,    2*44,   1*88 or  4*22 )

Mmm one must be neg and one must be positive because they mult to a negative.

these numbers must also add to +3.   that means the 'bigger' one is positive.

must be +11 and -8

(x+11)(x-8)=0

x+11=0   or   x-8=0

x=-11       or    x=8

Melody  Mar 31, 2015
Sort:

#1
+91510
+5

\$\$\\x^ 2 +3x-8=80\\\\
x^ 2 +3x-88=0\\\\\$\$

now I need two numbers that multiply to -88

(forgetting about the minius sign it could be    8*11,    2*44,   1*88 or  4*22 )

Mmm one must be neg and one must be positive because they mult to a negative.

these numbers must also add to +3.   that means the 'bigger' one is positive.

must be +11 and -8

(x+11)(x-8)=0

x+11=0   or   x-8=0

x=-11       or    x=8

Melody  Mar 31, 2015

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