Customers of a phone company can choose between two service plans for long distance calls. The first plan has a $
28

monthly fee and charges an additional
$
0.07

for each minute of calls. The second plan has no monthly fee but charges
$
0.11

for each minute of calls. For how many minutes of calls will the costs of the two plans be equal?

step-by-step explanation:

my butt

i think it would be 42cm

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

so, converting firstly the mixed fractions to improper fractions and then "adding".