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9-(-3)=?
-1-(-2)=?

9-(-3)=9+3=12    -1-(-2)=-1+2=1

Step-by-step explanation:

-(-x)=+x

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Answer & Step-by-step explanation:

Two negatives makes a positive, so change the symbol to a positive:

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Two negatives makes a positive, so change the negative 1 'minus negative' two to an addition sign:

x = ±sqrt(10)

step-by-step explanation:

5 - 2x² = -15

subtract 5 from each side

5-5 - 2x² = -15-5

-2x^2   = -20

divide by -2 on each side

-2x^2   /-2= -20/-2

x^2 =10

take the square root on each side

sqrt(x^2 )=±sqrt(10)

x = ±sqrt(10)

check:

5 - 2x² = -15

+sqrt(10)

5 - 2(sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15

-sqrt(10)

5 - 2(-sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15