Question

the average (arithmetic mean) of a,b&c 6, a-b=4 & ab=21. what is the value of c?​

Answer 1

Answer:

c = 8

Step-by-step explanation:

avg. arithmetic mean of a,b& c = 6

(a + b + c)/3 = 6

a + b + c = 18 --(1)

a - b = 4 --(2)

on squaring both sides ,we get

a^2 + b^2 - 2ab = 16

(a + b)^2 - 4ab = 16

(a+b)^2 - 4(21) = 16

(a + b)^2 = 100 => a + b = 10

from(1) => c = 18 - 10 = 8

Answer 2

Step-by-step explanation:

average arithmetic mean=a+b+c/3=6

a+b+c=18

given

a-b=4

find the value of either b or a from the given equation

a=4+b

put this above value in ab=21

(4+b)b=21

4b+b^2=21

arrange the equation in order

b^2+4b-21=0

b^2+7b-3b-21=0

b(b+7)-3(b+7)=0

(b-3)(b+7)=0

b=3;b=-7

now like we find the value of a

then put the values and put in the above first equation and get the answer.....