Question

Cho \(\dfrac{x+16}{9}\)=\(\dfrac{y-25}{-16}\)=\(\dfrac{z+49}{25}\) và 4x\(^3\)-3=29. Giá trị của biểu thức A=x+2y+3z là...

Answer 1

\(4x^3-3=29\Rightarrow x^3=\dfrac{29+3}{4}=8\Rightarrow x=\sqrt[3]{8}=2\)

Thay số: \(\dfrac{x+16}{9}=\dfrac{2+16}{9}=2\)

Suy ra: \(y=\left(-16\right)\cdot2+25\Leftrightarrow y=-7\) và \(z=25\cdot2-49\Leftrightarrow z=1\)

\(A=x+2y+3z\Leftrightarrow2+\left(-14\right)+3=-9\)

Answer 2

\(4x^3-3=29\Rightarrow x^3=\dfrac{32}{4}=2^3\Rightarrow x=3\)

\(\dfrac{19}{9}=\dfrac{2y-2.25}{-32}=\dfrac{3z+49.3}{75}=\dfrac{2y+3z+49.3-25.2}{75-32}=\dfrac{2y+3z+97}{43}\)

\(\dfrac{\left(2y+3z+3\right)+94}{43}=\dfrac{19}{9}\) \(\Rightarrow\left(x+2y+3z\right)=\dfrac{43.19}{9}-94\)

Answer 3

-9