81a²-25 would be the answer I'm pretty sure. Hopefully I helped.
x=3, you can find this by using finding common bases for equation b because 243=3^5. Because of that you can get rid of three on both sides to get the equation 2x-1=5 and then just solve for x to get x=3. For the first equation 5^3=625 so that also proves x=3.
Sorry if my explanation is a little disorganized if you need more help feel free to ask
Answer:
- <em>To solve these first swap x and y, solve for y and name it inverse function</em>
3. <u>y = -8x + 2</u>
- x = -8y + 2
- 8y = -x + 2
- y = -x/8 + 2/8
- y = -(18)x + 1/4
f⁻¹(x) = -(18)x + 1/4
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4.<u> y = (2/3)x - 5</u>
- x = (2/3)y - 5
- (2/3)y = x + 5
- y = (3/2)x + (3/2)5
- y = 1.5x + 7.5
f⁻¹(x) = 1.5x + 7.5
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5. <u>f(x) = 2x² - 6</u>
- x = 2y² - 6
- 2y² = x + 6
- y² = 1/2x + 3
- y =

f⁻¹(x) = 
-----------------------------------------
6. <u>y = (x - 3)²</u>
- x = (y - 3)²
= y - 3- y = 3 +

f⁻¹(x) = 3 + 
8% I am sorry if I am wrong