Question

Jak z podanego poniżej wzoru wyznaczyć literę r ?

P=πr(r+l)

Answer 1

 

P = πr(r+l)

P = πr² + πlr

πr² + πlr - P = 0

 

Δ = b² - 4ac

Δ = π²l² - 4πP

 

r = -b + √Δ/2a

r = -l + √π²l² - 4πP/2 x π

 

 

 

 

 

 

 

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Answer 2

P = πr(r+l)

P = πr²+πrl

πr²+πlr-P = 0 

a = π,  b = πl,  c = -P

Δ = b²-4ac = (πl)²-4·π·(-P) = π²l²+4πP = π(πl²+4P)

√Δ = √[π (πl²+4P)]

r = (-b+√Δ)/2a = [-πl+√((πl²+4P))]/2π = -l/2 + √((π(l²+4P)/4π²)) = -l/2 + √(((l²+4P)/2π))

r = -l/2 + √((l²+4P)/2π))