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

need help with this question#20
How many hydrogen atoms are represented in the formula (CH3)2CH2?
Expand the expression 2(r - 4) + 5(r + 2). Express your answer in simplest form
Approximately how many miles apart are Petrograd and Moscow ? A. 200 B. 350 C. 500 D. 650
13 squared? how does it mean and what is the solution?
what are the factor pairs of 38
need help with this question#20
what is the percent notation for 6.4%
ray wants the larger of two aquariums.One aquarium has 20 in. by 20 in. and has a height of 18 inches.The other aquarium has a base that is 40 in. by 12in. and
What is the velocity of an object that has a mass of 2.5 kilogram and a momentum of 1,000 kg·m/sec?