algebra

I create the function equation.

$2x+86y+17=-4\\ 86y=-2x-21\\ \color{blue}f(x)=y=-\dfrac{1}{43}x-\dfrac{21}{86}$

I determine the zero of the function.

$f(x)=y=-\dfrac{1}{43}x-\dfrac{21}{86}=0\\ x=- \dfrac{21}{86}\cdot 43\\ \color{blue}x_0 =-10.5$

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