Question

A supra b egal cu 7 supra 5
4a+3b=60
Urgent!!!

Answer 1

Răspuns:

$\boxed{\bf a =\dfrac{420}{43}}$

$\boxed{\bf b = \dfrac{300}{43}}$

Explicație pas cu pas:

Salutare!

$\it~~~$

$\bf \dfrac{a}{b}=\dfrac{7}{5} \implies\boxed{\bf 5a = 7b}$

$\bf 4a+3b = 60$

Vom inmulti prima relatie cu 4 si a doua relatie cu 5

$\bf 5a = 7b~~\bigg|\cdot4 \implies \boxed{\bf 20a =28b}$

$\bf 4a+3b = 60~~\bigg|\cdot5\implies \boxed{\bf20a+15b=300}$

Inlocuim pe 20a in a doua relatie

$\bf 28b+15b = 300\implies43b = 300\implies \boxed{\boxed{\bf b = \dfrac{300}{43} }}$

$\bf 5a = 7\cdot \dfrac{300}{43}\implies 5a = \dfrac{2100}{43}\implies43\cdot50= 2100$

$\bf \implies 43\cdot a= 420\implies \boxed{\boxed{\bf a =\dfrac{420}{43} }}$

$\it~~~~$

$\it Verificare:$

$\it \dfrac{a}{b}=\dfrac{\dfrac{420}{43} }{\dfrac{300}{43}} =\dfrac{420}{43}:\dfrac{300}{43}=\dfrac{\not420}{\not43}\cdot\dfrac{\not43}{\not300}=\dfrac{7}{5}~(adevarat)$

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