What two numbers multiply to -40 and add to 10

5 + sqrt(65), 5 - sqrt(65)

Step-by-step explanation:

x + y = 10

x×y = -40

so, two equations with 2 variables. using one equation to express one variable by the second. and then using the second equation to solve and calculate the second variable. and then by knowing the second variable we calculate the first.

=> x = 10 - y

=> (10-y)×y = -40

=> -1×(10-y)×y = 40

=> (y-10)×y = 40

=> y^2 - 10×y - 40 = 0

remember the solution for a quadratic equation

a×x^2 + b×x + c

is

x = (-b ± sqrt(b^2 - 4×a×c)/(2×a)

in our case

a = 1

b = -10

c = -40

and we used "y".

so,

y = (--10 ± sqrt((-10)^2 - 4×1×(-40))/(2×1) =

= (10 ± sqrt(100 + 160))/2 = (10 ± sqrt(260))/2 =

= (10 ± sqrt (4×65))/2 = 10/2 ± 2×sqrt(65)/2 =

= 5 ± sqrt(65)

=>

for y = 5 + sqrt(65), x = 10 - 5 - sqrt(65) = 5 - sqrt(65)

for y = 5 - sqrt(65), x = 10 - 5 + sqrt(65) = 5 + sqrt(65)

a

step-by-step explanation:

the height of the surface increases from the center out to the sides of the road.

step-by-step explanation:

as we move out we move away from the x-axis.

and as mentioned in the problem statement that height of a road increases when we move away from the center x.

hence proved that 3rd option

the height of the surface increases from the center out to the sides of the road.

is the correct option.