Question

Problem:

Answer 1

Answer:

a)

We know that:

a, b > 0

a < b

With this, we want to prove that a^2 < b^2

Well, we start with:

a < b

If we multiply both sides by a, we get:

a*a < b*a

a^2 < b*a

now let's go back to the initial inequality.

a < b

if we now multiply both sides by b, we get:

a*b < b*b

a*b < b^2

Then we have the two inequalities:

a^2 < b*a

a*b < b^2

a*b = b*a

Then we can rewrite this as:

a^2 < b*a < b^2

This means that:

a^2 < b^2

b) Now we know that a.b > 0, and a^2 < b^2

With this, we want to prove that a < b

So let's start with:

a^2 < b^2

only with this, we can know that a*b will be between these two numbers.

Then:

a^2 < a*b < b^2

Now just divide all the sides by a or b.

if we divide all of them by a, we get:

a^2/a < a*b/a < b^2/a

a < b < b^2/a

In the first part, we have a < b, this is what we wanted to get.

Another way can be:

a^2 < b^2

divide both sides by a^2

1 < b^2/a^2

Let's apply the square root in both sides:

√1 < √( b^2/a^2)

1 < b/a

Now we multiply both sides by a:

a < b