<span>Square root of 100 is a rational number. Because sqaure rooot 100 = 10. And, 10 can be written in the form rational number. Any number that can be written in the form of p/q where p and q are integers and q in not zero is called a rational number.</span>
<u>Answer:</u>
The equation of a polynomial of degree 3, with zeros 1, 2 and -1 is 
<u>Solution:</u>
Given, the polynomial has degree 3 and roots as 1, 2, and -1. And f(0) = 2.
We have to find the equation of the above polynomial.
We know that, general equation of 3rd degree polynomial is

where a, b, c are roots of the polynomial.
Here in our problem, a = 1, b = 2, c = -1.
Substitute the above values in f(x)


So, the equation is 
Let us put x = 0 in f(x) to check whether our answer is correct or not.

Hence, the equation of the polynomial is 
X² - 169 = 0
x = ?
<span> Add 169 to both sides.
</span>
x² <span>− 169 + 169 </span>= <span>0 + 169</span>x² = 169
Square root
x = <span>± <span>√<span>169
</span></span></span>
<span><span>x = <span><span>13<span> or </span></span>x </span></span>= <span>−13
x can be 13 or -13.</span></span>
Answer:
Here Two triangles BDE and BAC are similar as mentioned
So, According to Similarity of triangles theorem
BE/BC = DE/AC
4/16= x/20
1/4 = x/20
x= 20/4
x=5