# How to solve an equation given certain parameters?

I am new to Mathematica so please bear with me. I have an equation that has around 7 parameters and one unknown. I was able to use FindRoot to solve it; however, I want to do the same for around 1000 rows of parameters. I usually do this in Excel were I just drag down the same command for all rows to get the result for each row. I tried to use the Table, Matrix, and other commands but couldn't understand how it works. I think there is something wrong with my understanding on how Mathematica works. Any suggestions on guiding me is greatly appreciated.

Edit#1

For example,

a b c f(x)=ax^2+bx+c Findroot f(x)

2 3 3 f(x)=2x^2+3x+3 ?

2 2 1 f(x)=2x^2+2x+1 ?

5 3 5 f(x)=5x^2+3x+5 ?

. . . . .

. . . . .

. . . . .

2 8 3 f(x)=2x^2+8x+3 ?

Edit#2

I tried the following as suggested by @belisarius ;however, i get " FindRoot::nveq: The number of equations does not match the number of variables in "

params = {{{61.07213, 118.844, 127.4626, 133.3232, 140.4969, 154.6745, 0.0725203, 0.0459785, 0.0538076, 0.1009101, 0.1382398, -0.0140873}, {349.7488, 115.493, 114.1906, 112.2911, 110.223, 108.051, 0.1205766, 0.1778708, 0.1969301, 0.2107067, 0.2875397, -0.0140873}, {579.7379, 332.051, 383.5087, 437.5052, 493.8236, 556.8684, 0.2324231, 0.2111662, 0.1930639, 0.1914745, 0.2012774, -0.0140873}}};

f[{m_, b0_, b1_, b2_, b3_, b4_, roe1_, roe2_, roe3_, roe4_, roe5_, gCT_}] := FindRoot[b0 + (b0 (-R + roe1))/(1 + R) + ( b1 (-R + roe2))/(1 + R)^2 + (b2 (-R + roe3))/(1 + R)^3 + ( b3 (-R + roe4))/(1 + R)^4 + ( b4 (-R + roe5))/(1 + R)^5 + ((1 + gCT) b4 (-R + roe5))/((1 + R)^5 (-gCT + R)) - m, {R, 0}]

f /@ params

Any ideas on why I get this result?

• "...bare with me."? Do I really need to get naked? ;-} And what you're after will be in the Map and Apply families. See the docs. for more info.
– ciao
Jul 15, 2015 at 4:31
• It might not seem like it, but for a new user you may have picked a problem that is a little too difficult. Imagine being new to Excel. How much would you have needed to learn to do this problem? Now study this example: params = {{a, b, c}, {2, 3, 3}, {2, 2, 1}}; f[{p1_, p2_, p3_}] := x /. Solve[p1*x^2 + p2*x + p3 == 0, x]; Map[f, params] Look up each of those functions in the help system and read until you understand it. There is a lot to learn to be able to do something like this.
– Bill
Jul 15, 2015 at 5:30
• @Bill Impressive, isn't it? That's why many people abandon Mma: the learning curve Jul 15, 2015 at 5:34
• @Bill Thank you very much, that really help me. Jul 15, 2015 at 5:58
• In your edited example you have triple curly braces in param. You should have only two levels Jul 15, 2015 at 7:14

(*First we defime our "rows"*)
params = {{2, 3, 3}, {2, 2, 1}, {5, 3, 5}};

(*Now we define a function of the params that solves the equation*)
f[{a_, b_, c_}] := Solve[a x^2 + b x + c == 0, x]

(*and we apply the function to each parameter set at a time*)
f /@ params // Column
(*
{{{x -> 1/4 (-3 - I Sqrt[15])}, {x -> 1/4 (-3 + I Sqrt[15])}},
{{x -> -(1/2) - I/2}, {x -> -(1/2) + I/2}},
{{x -> 1/10 (-3 - I Sqrt[91])}, {x -> 1/10 (-3 + I Sqrt[91])}}}
*)