agentkronus
agentkronus agentkronus
  • 02-03-2015
  • Mathematics
contestada

Find x when P = 21.

P = x(x - 1) / 2

Respuesta :

konrad509
konrad509 konrad509
  • 02-03-2015
[tex]21=\dfrac{x(x-1)}{2}\\ 42=x^2-x\\ x^2-x-42=0\\ x^2+6x-7x-42=0\\ x(x+6)-7(x+6)=0\\ (x-7)(x+6)=0\\ x=7 \vee x=-6[/tex]
Answer Link

Otras preguntas

When MgCO3(s) is strongly heated, it produces solid MgO as gaseous CO2 is driven off.Does the oxidation number of carbon change upon the formation of CO2?
what does como eres tu mean in spanish?
can u tell me how to solve this promblem 4/7 plus 3/7
Two diverging light rays, originating from the same point, have an angle of 5° between them. After the rays reflect from a plane mirror, what is the angle betwe
which of the following expressions does not equal: the sixth root of 81x^4y^8 a. (3xy^2)^2/3 b. (3x)^2/3y^4/3 c. (3x^2y^4)^1/3 d. cube root of 9x^2y^4
write an equation that is perpendicular to the line y = 2x + 13?
which foods earthworms can digest?
lara has a tin of peanuts cashews and pecans she will pick a second nut without looking. how many outcomes are there for her two picks?
How would you define psychological realism?
List all integers between -0.6 and 4.17 THANK U