How to find f(x)*g(x)

Hi!

If i have f(x) = 1 + x and g(x) = 1 - x, i want to find h(x) = f(x)*g(x) = (1+x)*(1-x)=1-x.^2 What should i do?

Thanks!

Answer 1

[Star Strider]

It looks like you already did it. To code it using anonymous functions:

f = @(x) 1 + x;
g = @(x) 1 - x;
h = @(x) f(x).*g(x);

x = linspace(-10, 10);

figure(1)
plot(x, f(x), x, g(x), x, h(x))
grid
legend('f(x)', 'g(x)', 'h(x)', 'Location', 'south')

[Tran]

Thank you Star Strider! But i want to receive and to show function h(x) = 1 - x.^2.

[Star Strider]

My pleasure!

Sorry, I misunderstood.

What you want would be:

h = @(x) 1 - x.^2;

The dot before the (^), i.e. (.^) ,denotes an element-wise operation, so x can be a scalar, vector or matrix and the function will still work.

[James Tursa]

What are you starting with? Strings for f(x) and g(x)? Or what?

[Tran]

I am starting with strings for f(x) and g(x), so i want to receive string h(x) = f(x)*g(x) = 1-x.^2. I have done it easy in Mathematica, but in Matlab i don't know what should i do? Thanks!

[James Tursa]

What do you want to end up with for h? Another string? Or a symbolic expression? Or a function handle using the dot operators (.* , ./ , .^ )?

[Tran]

Hi James ! I want to receive a symbolic expression h(x) = 1 - x.^2 , because i don't need calculate the expression, i only want to know components in the expression.

[Star Strider]

In that instance, use the Symbolic Math Toolbox.

[Tran]

Thank you so much Star Strider, i think this is what i want to find.

[James Tursa]

E.g.,

>> f = '1+x'
f =
1+x
>> g = '1-x'
g =
1-x
>> syms x
>> fx = eval(f)
fx =
x + 1
>> gx = eval(g)
gx =
1 - x
>> hx = simplify(fx*gx)
hx =
1 - x^2

[Tran]

Thank you so much James Tursa!

[Star Strider]

@James — Thank you!

@Tran — My pleasure!

Answer 2

[Tanveer ul haq]

syms x
f = 1 + x;
g = 1 - x;
h = simplify(f*g)

[John D'Errico]

Note that this does not actually solve the problem as asked.