Question

$2x - 3y = - 5 \\ {4x}^{2} - {9x}^{2} = 20 \\ 2x + 3y = ...$
​Dau coroană

Answer 1

Răspuns:

2x-3y= -5

4x²-9y²=20

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Aplici formula

A²-B²=(A-B)(A+B) unde A²=4x²   B²=9y²

4x²-9y²=20

(2x-3y)(2x+3y)=20

(-5)(2x+3y)=20║:-5

2x+3y=-4

Explicație pas cu pas:

Answer 2

$\it 2x-3y=-5\ \ \ \ \ (*)\\ \\ 4x^2-9y^2=20 \Rightarrow 2^2x^2-3^2y^2=20 \Rightarrow (2x)^2-(3y)^2=20 \Rightarrow\\ \\ \Rightarrow (2x-3y)(2x+3y)=20 \stackrel{(*)}{\Longrightarrow} -5(2x+3y)=20|_{:(-5)} \Rightarrow 2x+3y=-4$