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# Help :D

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Hello, can someone help me with this  tasks?

1.)

$$\log _2\left(x\right)-\log _4\left(y\right)=0$$

$$5x^2-y^2=4$$

2.)

$$64\cdot 9^x-84\cdot 12^x+27\cdot 16^x=0$$

Jun 18, 2018
edited by Guest  Jun 18, 2018

#1
+1

2)

Solve for x:
64 9^x - 7 12^(x + 1) + 27 16^x = 0

The left hand side factors into a product with two terms:
(16 3^x - 9 4^x) (4 3^x - 3 4^x) = 0

Split into two equations:
16 3^x - 9 4^x = 0 or 4 3^x - 3 4^x = 0

Add 9 4^x to both sides:
16 3^x = 9 4^x or 4 3^x - 3 4^x = 0

9 4^x = 2^(2 x)·3^2:
2^4·3^x = 2^(2 x)·3^2 or 4 3^x - 3 4^x = 0

Equate exponents of 2 and 3 on both sides:
4 = 2 x and x = 2 or 4 3^x - 3 4^x = 0

All equations give x = 2 as the solution:
x = 2 or 4 3^x - 3 4^x = 0

Add 3 4^x to both sides:
x = 2 or 4 3^x = 3 4^x
3 4^x = 2^(2 x)·3^1:
x = 2 or 2^2·3^x = 2^(2 x)·3^1

Equate exponents of 2 and 3 on both sides:
x = 2 or 2 = 2 x and x = 1

All equations give x = 1 as the solution:

x = 2       or       x = 1

Jun 18, 2018
#2
+1

1)

Log_2(x) - Log_4(y) = 0....................(1)
5x^2 - y^2 =4..................................(2)
x = ± sqrt(y^2 + 4)/sqrt(5)       sub this into (1) above.
Solve for y:
log(sqrt(y^2 + 4)/sqrt(5))/log(2) - log(y)/log(4) = 0

Bring log(sqrt(y^2 + 4)/sqrt(5))/log(2) - log(y)/log(4) together using the common denominator log(2) log(4):
(log(4) log(sqrt(y^2 + 4)/sqrt(5)) - log(2) log(y))/(log(2) log(4)) = 0

Multiply both sides by log(2) log(4):
log(4) log(sqrt(y^2 + 4)/sqrt(5)) - log(2) log(y) = 0

log(4) log(sqrt(y^2 + 4)/sqrt(5)) - log(2) log(y) = log(y^(-log(2))) + log(5^(-log(2)) (y^2 + 4)^log(2)) = log(5^(-log(2)) y^(-log(2)) (y^2 + 4)^log(2)):
log(5^(-log(2)) y^(-log(2)) (y^2 + 4)^log(2)) = 0

Cancel logarithms by taking exp of both sides:
5^(-log(2)) y^(-log(2)) (y^2 + 4)^log(2) = 1

Multiply both sides by 5^log(2):
y^(-log(2)) (y^2 + 4)^log(2) = 5^log(2)

Factor out the common power log(2) from the left hand side:
((y^2 + 4)/y)^log(2) = 5^log(2)
Raise both sides to the power of 1/log(2):
(y^2 + 4)/y = 5

Multiply both sides by y:
y^2 + 4 = 5 y

Subtract 5 y from both sides:
y^2 - 5 y + 4 = 0

The left hand side factors into a product with two terms:
(y - 4) (y - 1) = 0

Split into two equations:
y - 4 = 0 or y - 1 = 0

y = 4 or y - 1 = 0
y = 4            or          y = 1        and          x =+or- 2         or              x=+or- 1

Jun 18, 2018
#3
+1

Thanks :D

Jun 18, 2018