Year 12s: what will be the first way you research your future options? >>

Year 12s: what will be the first way you research your future options? >>

Year 12s: what will be the first way you research your future options? >>

Logarithms

Custardcream000

Solve the equation, 5^2x - (16 x 5^x) +63 = 0

Is this correct:

let 5^x = u

u^2 - 16 u +63 = 0

(u-7)(u-9)

5^x = 7 or 9

x log 5 = log63
x= log 63 /log 5

Original post by Custardcream000

Solve the equation, 5^2x - (16 x 5^x) +63 = 0

Is this correct:

let 5^x = u

u^2 - 16 u +63 = 0

(u-7)(u-9)

5^x = 7 or 9

x log 5 = log63
x= log 63 /log 5

The bold line above means that 5^x can be 7 or can be 9.

So you have two equations:

5^x = 7

5^x = 9

Solve both to get two solutions.

Custardcream000

OP

Original post by notnek

The bold line above means that 5^x can be 7 or can be 9.

So you have two equations:

5^x = 7

5^x = 9

Solve both to get two solutions.

thanks

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