The temperature at a point (x, y) on a flat metal plate is given by t(x, y)=19/(2+x^2+y^2), where t is measured in celsuis and x, y in meters. find the rate of change of temperature with respect to distance at the point (1,2) in the following directions.
(a) the x-direction
(b) the y-direction

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In the figure below, ∠dec ≅ ∠dce, ∠b ≅ ∠f, and segment df is congruent to segment bd. point c is the point of intersection between segment ag and segment bd, while point e is the point of intersection between segment ag and segment df. the figure shows a polygon comprised of three triangles, abc, dec, and gfe. prove δabc ≅ δgfe.

What is the value of x in the this question ?