Timed test, the series using sigma notation. 1 + 4 + 16 + + 256.

the answer here should be sigma(4^x), with the x value on the bottom being 0 and the top being 4.

to find this, we have to determine what could give us numbers going up by these increments. since it is growing increasingly, we know it is an exponential. we can then tell they are all multiples of 4. from there, to find the starting x and ending x, we simply have to find the power of 4 in the first and last numbers.

1 = 4^0

256 = 4^4

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