Hiro bought a five-pack of rechargeable batteries last week and an eight-pack
of the same type of batteries this week. He knows the cost of each battery is
the same no matter how many are in a pack. If Hiro spent $5.55 more on the
eight-pack than on the five-pack, how much would a ten-pack cost?

Step-by-step explanation:

Let x represent the cost of each battery since the cost of each battery is the same no matter how many are in a pack.

Hiro bought a five-pack of rechargeable batteries last week and an eight-pack of the same type of batteries this week. It means that the cost of the 5 pack battery is $5x and the cost of the 8 pack battery is $8x.

If Hiro spent $5.55 more on the

eight-pack than on the five-pack, it means that

8x = 5x + 5.5

8x - 5x = 5.5

3x = 5.5

x = 5.5/3 = 1.83

The cost of a 10 pack battery would be

1.83 × 10 = $18.3

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