Question

determine o valor de y das expressões abaixo:

a)y=10+×+9-2×para×=3

b)y=x2-4x-3×+8para×=-1

c)y=x3-2×+1para×=-2

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Answer 1

a)

$\begin{bmatrix}y=10+x+9-2x\\ x=3\end{bmatrix}\\\\\begin{bmatrix}x=3\end{bmatrix}\\\\y=10+3+9-2\cdot \:3\\\\y=16\\\\y=16,\:x=3$

b)

$\begin{bmatrix}y=x^2-4x-3\times \:+8\\ x=-1\end{bmatrix}\\\\\begin{bmatrix}x=-1\end{bmatrix}\\\\y=\left(-1\right)^2-4\left(-1\right)-3\times \:+8\\\\=\left(-1\right)^2+4\times \:1-3+8\\\\1+4-3+8=10\\\\=10\\\\y=10,\:x=-1$

c)

$\begin{bmatrix}y=x^3-2x+1\\ x=-2\end{bmatrix}\\\\\begin{bmatrix}x=-2\end{bmatrix}\\\\y=\left(-2\right)^3-2\left(-2\right)+1\\\\=\left(-2\right)^3+2\cdot \:2+1\\\\5-8=-3\\\\=-3\\\\y=-3,\:x=-2$