Alan

They are generally called the semi-major axis and the semi-minor axis.

5x4 is not 9 !!!

5x4x10³ → 20x10³ → 2x10⁴

cosh² - sinh² = 1

cosh x = sqrt(1 + (16/63)²) = sqrt(4225/3969) = 65/63

tanh = sinh/cosh

tanh x = 16/65

coth = 1/tanh,   sech = 1/cosh, csch = 1/sinh 

etc.

We must have:  (x + 3)(kx - a) = 0

So:  kx² + (3k-a)x - 3a = 0. 

Compare term by term with kx² -2x - 3 = 0

Clearly a = 1, so 3k - 1 = -2

3k = -1

k = -1/3

.

"At Jessie's fruit stall, 280 apples were sold in the morning and 3/5 of the remaining apples were sold in the afternoon. As a result, the number of apples left became 1/6 of the total apples at first. Given that the apples were sold at $2.50 in packs of six apples, how much did Jessie receive from the sale of the apples in the afternoon?"

.

You are quite right.  A typo on my part!

.

Using cos² = 1 - sin² 

cos²A = 1 - 5/25 = 20/25   so   cosA = 2√5/5

cos²B = 1 - 1/25 = 24/25   so   cosB = 2√6/5

cos(B-A) = cosBcosA + sinBsinA

sin(B-A) = sinBcosA - sinAcosB

Can you take it from here?

Guest#1 beat me to it, but here's my answer anyway:

You would need to know the volume, V, then the mass will be V/v. (v is specific volume)

.

Probably better to add sqrt(x-2) to both sides and subtract sqrt(x+1) from both sides first, before thinking about squaring!