Question

i need help with sequences and series

Answer 1

If AM and GM of roots of a quadratic eqn are 8 and 5 repectively

Answer 2

obtain the quaqdratic eqn

Answer 3

seris lol ....Arithmetic progression and Geometric progression

Answer 4

(a + b) = 2*8

ab = 5^2 = 25

x^2 + x(a+b) + ab=0
x^2 + 16x + 25=0

Answer 5

ya ishaan thats wat i thought but the answer is x^2-16x+25

Answer 6

i dont understand how!!!

Answer 7

http://www.wolframalpha.com/input/?i=x^2+-+16x+%2B+25%3D0

http://www.wolframalpha.com/input/?i=x^2+%2B+16x+%2B+25%3D0

Answer 8

To get a + b =16, we need -16x not 16x

Answer 9

ya thats my doubt in ncert text it is written x^2-16x+25=0

Answer 10

also refer this http://cbse.meritnation.com/study-online/solution/Math/w3CmXdPzZP8gM$VT5Rpfjg!!

Answer 11

ab=25
a+b=16
so,
b=25/a
substitute
in 2nd equation to get
a^2-16a+25
a is root
so it is x
x^2-16x+25
is my method rite?

Answer 12

yeah that is good king

Answer 13

thnx ishaan!

Answer 14

ya but y the othr method fails????

Answer 15

i didnt understand the other method.......

Answer 16

probably because we assumed that a and b are positive

Answer 17

and that isn't always true

Answer 18

gud point!!!!!

Answer 19

but for above condition a and b shud be +ve u see a+b=16

Answer 20

so?a might be 36 and b might be -20

Answer 21

i think it must be

x^2 + x | sum of roots| + product of roots = 0

Answer 22

ya y it fails????

Answer 23

a+b is in my case 16
36-20=16

Answer 24

hey man product shud be 25!!!

Answer 25

oh sry i frgt!!!

Answer 26

cnfusing!!!

Answer 27

sqrt(ab) = 5 right?

now when we square, we ignore the possibility that both a and b must be negative, - * - = +

Answer 28

can* not must

Answer 29

oh yeah !!!!ure rite!!

Answer 30

but y we got crxt answr othr way??

Answer 31

hey we shud only take positive root as G M = sqrt (Ab)

Answer 32

+ve sqrt

Answer 33

exactly

Answer 34

:(((

Answer 35

so?????

Answer 36

roots are 8 - sqrt39 and 8 + sqrt39

8 - sqrt39 + 8 + sqrt39 = 16
(8 - sqrt39)(8 + sqrt39) = (sqrt39 - 8)(sqrt39 + 8) = 39 - 16 = 25

Answer 37

:(

Answer 38

wer hav we gone wrong???

Answer 39

so??

Answer 40

so it can be +ive or -ive

Answer 41

WAT A TERRIBLE QN!!!

Answer 42

HELPPPPPPP

Answer 43

for +16x

x^2 + 16x + 39 = 0
x^2 + 2*8x + 64 = 64 - 39
(x + 8 )^2 = 25

x + 8 = |5|

x = - 13
or

x = -3

Answer 44

-13 + (-3) = -16

Answer 45

Sorry I solved it the other way

Answer 46

x + 8 = |sqrt39|

Answer 47

x = -sqrt39 - 8

x = sqrt39 - 8

for x^2 + 16x +25 = 0

Answer 48

x^2 - 16x + 25 = 0

x - 8 = |sqrt39|

x = 8 - sqrt39
or
x = 8 + sqrt39

Answer 49

the roots are a and b
so the factors are (x-a) and (x-b)

-> (x-a)(x-b) = x^2 -(a+b)x + ab

Answer 50

Oh okay thanks chris!



I can't believe we were committing such a stupid error

Answer 51

:)