9. Jack has $5.90 in spare change in his pocket. All of the coins are nickels and quarters. If he has 50 coins total, how many of each coin does he have? (Use a system of equations
to solve algebraically. Identify your variables.)

33 nickels, 17 quarters

Step-by-step explanation:

q=quarters, n=nickels

Since total number of coins = 50 and he only has quarters and nickels,

q + n = 50.

Since a quarter is 0.25 dollars, a nickel is 0.05 dollars, and his total is $5.90,

0.25q + 0.05n = 5.90

Multiply the entire second equation by -4 to get -q and eliminate q from both equations: -4(0.25q + 0.05n = 5.90)

So, q + n = 50

And -q -0.2n = -23.6

Cancel q's and add down to combine both equations, so 0.8n = 26.4

Solve for n by dividing 0.8 by both sides, so n = 33

Plug n back into the first equation: q + 33 = 50 and q is thus 17.

Hope this helps!

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