Question

Bună,ma puteti ajuta la 3,4,5?
Dau 80 de puncte,va rog mult.​

Answer 1

Răspuns:

Explicație pas cu pas:

3)

( 1/√2 + 1/√3) × ( 1/√2 - 1/√3) = 1/6

-> inmultesc fiecare termen al parantezei cu termenii diferentei

= 1/√2 × 1/√2 + 1/√3 × 1/√2 - 1/√2 × 1/√3 - 1/√3 × 1/√3 =

= 1/√4 + 1/√6 - 1/√6 - 1/√9 =

= ³⁾1/2 - ²⁾1/3 =

= 3/6 - 2/6 =

= 1/6

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4)

x/y = 3/8 ⇒ 8 x = 3 y → produsul mezilor = produsul extremilor

⇒x/3 = y/8 = k → coeficient de proportionalitate

⇒  x = 3 k   si  y = 8 k

( 2 x + 3 y ) / ( 3 x + 2 y ) = 6/5

= (2×3k + 3 ×8k ) / ( 3×3k + 2×8k) =

= ( 6 k + 24 k ) /( 9 k + 16 k ) =

= 30 k/25 k =

-> simplific fractia cu 5, iar k/k = 1

= 6/5

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5)

( x+2)² + 2(x-5)(x+5) = 3(x-1)² + 1

x² + 4 x + 4 + 2(x² - 25) = 3 ( x² - 2 x + 1 ) + 1

x² + 4 x + 4 + 2 x² - 50 = 3 x² - 6 x + 3 + 1

( x² + 2 x²) + 4 x - 46 = 3 x² - 6 x + 4

3 x² + 4 x - 3 x² + 6 x = 4 + 46

10 x = 50

x = 50 : 10

x = 5