Question

(1). Solve 3^x – 4 = 7^x + 9

x ≈ –25.86

x ≈ –2.59

x ≈ –0.39

x ≈ –0.04



(2). Solve 5^x + 5 = 9^x
x ≈ –3.63

x ≈ –0.28

x ≈ 0.07

x ≈ 13.69

Answer 1

those choices are approximations so i'm assuming that you need to solve by graphing (calculator)?

Answer 2

no. not really if you look at the problem you will notice there are a like terms so this should break down and you don't need a graphing calc for this problem

Answer 3

to further show what I am talking because we have 3^x -4 +=7x^x +9 in this case we can see that the power of x is one because no value is given.

Answer 4

the answer should be given like the answers shown

Answer 5

ingore the extra x on 7^X it is a typo

Answer 6

\(\LARGE3^x-9=7^x+4\)

Answer 7

\(\LARGE3^x-3^3=7^x+4\)

Answer 8

@jiteshmeghwal9 one mistake it will be 3^2

Answer 9

\(\LARGE3^{x \over 2}=7^x+9\)
Ohhhh ! sorry thanx @mathslover :)

Answer 10

4*

Answer 11

No problem continue jitesh

Answer 12

\(\LARGE3^{x \over 2}=7^x+4\)

Answer 13

here comes the right problem :(

Answer 14

wht should we do further @mathslover @waterineyes ????

Answer 15

need ur help :)

Answer 16

\[3^x - 7^x = 13\]

Answer 17

\[\large{ 3^x – 4 = 7^x + 9}\]
\[\large{3^x-7^x=9+4}\]

Answer 18

so wht further ???
Need to solve for 'x'

Answer 19

http://www.wolframalpha.com/input/?i=solve+%3A3%5Ex-7%5Ex%3D9%2B4

wolfram has no step by step soln also

Answer 20

i also find out this

http://www.wolframalpha.com/input/?i=3^x-4%3D7^x%2B9

Answer 21

We have to go by plugging in the values from the answer choices and using calculator that is obvious..

Answer 22

we can not do by plugging in values since it don't have real soln

Answer 23

well if we turn bases same then can we do it as

\(3^x=9\)
\(3^x=3^2\)
\(x=2\)
?????

Answer 24

No no , i think there is involvement of logarithm here

Answer 25

hmmmm

Answer 26

We cannot evaluate log for :

\(log(a + b)\)..

Answer 27

Is there any formula for this ??

Answer 28

log(a + b) = log(a * (1 + b/a)) = log a + log(1 + b/a)

Answer 29

http://stackoverflow.com/questions/3974793/to-compute-logab

Answer 30

log(3^x) + log(1+7^x/3^x)

Answer 31

\[\large{xlog3 +log(\frac{3^x+7^x}{3^x})}\]

Answer 32

\[\large{x*log3 + log(3^+7^x)-log(3^x)}\]
\[\large{\cancel{xlog3}+log(3^x+7^x)\cancel{-log(3^x)}}\]

Proved :D

Answer 33

@vishweshshrimali5

Answer 34

How will you find :

\[\log(1 + \frac{b}{a})\]

Answer 35

They are still in addition..

Answer 36

simple :
\[\large{log(\frac{a+b}{a})}\]
\[\large{log(a+b)-log(a)}\]

Answer 37

And here how will you find:

\[\log(a + b)\]

Answer 38

that is the main problem

Answer 39

They are again addition..

Answer 40

Ha ha ha..

That is what I am saying..

Answer 41

:)

Answer 42

@waterineyes @mathslover and everyone else... well I am preparing for a competitive exam which has MCQs so I have got a sort of expertise in them and one of the way of solving questions which will be difficult to solve (like thisone) we usually plug in the values of the options and find out the correct answer and simply evaluate them using our common sense/..........
I think this will be the best method(for I have not tried solving it till now) for solving this question

Answer 43

I was saying the same..

Answer 44

but @vishweshshrimali5 the given values are too complex

Answer 45

would you like to find : 3^(-25.6) or anything else?

Answer 46

Or we are going to do that by guess?

Answer 47

we can use binomial theorem for 3^(x/2) and 7^(x)

Answer 48

Try smaller ones..
Ha ha ha..

Answer 49

.............

Answer 50

we can write \(7^x = (3+4)^x\)

Answer 51

:D @waterineyes

Answer 52

and then simplify them.......

Answer 53

:'(

Answer 54

for answer no. 1 its obvious that for 3^x - 7^x = 13

any real value of x is not going to satisfy it.............

Answer 55

right

Answer 56

and for 2nd 9^x - 5^x = 5
now its clear that for x<0 ;9^x <5^x so that would not work

Answer 57

so only 2 options remain

Answer 58

for x = 0.07 its clear that both 9^x and 5^x will be very very small to get their difference equal to 5

Answer 59

only option that remain is the last one

Answer 60

@waterineyes

Answer 61

The both questions are WRONG

Answer 62

Because 9 - 5 = 4 which is very close to 5
thus its clear that x should be close 1

Answer 63

So, the correct answer should be 1

Answer 64

@rayford you just fooled all of us ........ XD

Answer 65

@waterineyes got my point ?????????

Answer 66

@jiteshmeghwal9

Answer 67

Yeah I got @vishweshshrimali5

Answer 68

thanks for the medal everyone

:) gud @waterineyes

Answer 69

i'm sorry i fell asleep last night... so what answers would you suggest choosing vishweshshrimali5?

Answer 70

or someone else..

Answer 71

@rayford hi

See, as I have already mentioned the both questions are wrong, so there is no chance of saying which option is correct

Answer 72

for question 1, there is no such real value of x.
for question 2, the value of x to the nearest integer = 1

Answer 73

just throwing this out there..but you do realize the problem looks like this right?