I am trying to illustrate sum of functions. I have one function x*x - 8*x + 7 and another Log[2*x + 4.5] I understand that I must add all of coordinates both of these functions. I use function Plot : Plot[{x*x - 8*x + 7 && Log[2*x + 4.5]}, {x, -10, 10}] But it doesn't draw. Can you tell me how it must be. Thanks.
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1 Answer
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Your first function can have complex values for x < 0, so you can define:
f1[x_] := Re[x^x + 8 x + 7]; f2[x_] := Log[2 x + 4.4] and then plot the functions together with the sum:
Plot[{f1[x], f2[x], f1[x] + f2[x]}, {x, -1, 1}, PlotLegends -> "Expressions"] But with the range -10 < x < 10, you won´t see much left of the y-axis, due to the growth of the first function.
&&with a comma,. If you want to draw the literal mathematical sum, just replace&&with+. But note that the log will not be defined for x < -2.25. $\endgroup$