# exponential equation

• Oct 22nd 2008, 04:55 PM
Michelle Belford
exponential equation
I am practicing for my exams need help to see if i'm doing the right thing. Thank you

Determine the values of x in the following exponential equations:

(a)3x×27x + 81 = 729

(b)(23x)x + 32 = 1/256

5. Solve the following equations:

(e) y = 2x (f) 2x – y + 2 = 0
y = x2 + 1 4x + y – 5 = 0

(g) x – y = 0
5x – 3y = 10

• Oct 22nd 2008, 05:03 PM
vincisonfire
Do you mean
$\displaystyle {3 \cdot x}^{27 \cdot x} +81 = 729$???
• Oct 22nd 2008, 05:07 PM
Shyam
Quote:

Originally Posted by Michelle Belford
I am practicing for my exams need help to see if i'm doing the right thing. Thank you

Determine the values of x in the following exponential equations:

(a)3x×27x + 81 = 729

(b)(23x)x + 32 = 1/256

(a)3x×27x + 81 = 729

did you mean the exponential equation $\displaystyle 3^x \times 27^x +81 = 729 \;\;?$
• Oct 22nd 2008, 05:38 PM
Michelle Belford
YES U R CORRECT
• Oct 22nd 2008, 05:44 PM
vincisonfire
$\displaystyle 3^x \times 27^x +81 = 729$
$\displaystyle 3^x \times 3^{3\cdot x} = 729 - 81$
$\displaystyle 3^{x+3\cdot x} = 648$
$\displaystyle {4\cdot x} \cdot ln(3) = ln(648)$
$\displaystyle x = \frac{ln(648)}{4 \cdot ln(3)}$