math

$$ y_i=ax_i^2+bx_i $$

$$ y_j=ax_j^2+bx_j $$

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$$ y_ix_j=ax_i^2x_j+bx_ix_j $$

$$ y_jx_i=ax_j^2x_i+bx_ix_j $$

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$$ y_ix_j-y_jx_i=a(x_i^2x_j-x_j^2x_i) $$

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$$ a=\frac{y_ix_j-y_jx_i}{x_i^2x_j-x_j^2x_i} $$

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$$ y_ix_j^2=ax_i^2x_j^2+bx_ix_j^2 $$

$$ y_jx_i^2=ax_i^2x_j^2+bx_jx_i^2 $$

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$$ y_ix_j^2-y_jx_i^2=b(x_ix_j^2-x_i^2x_j) $$

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$$ b=\frac{y_ix_j^2-y_jx_i^2}{x_ix_j^2-x_i^2x_j} $$

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