# If a and b are roots of the equation x

Question:

If $a$ and $b$ are roots of the equation $x^{2}-x+1=0$, then write the value of $a^{2}+b^{2}$.

Solution:

Given: $x^{2}-x+1=0$

Also, $a$ and $b$ are the roots of the equation.

Then, sum of the roots $=a+b=-\left(\frac{-1}{1}\right)=1$

Product of the roots $=a b=\frac{1}{1}=1$

$\therefore(a+b)^{2}=a^{2}+b^{2}+2 a b$

$\Rightarrow 1^{2}=a^{2}+b^{2}+2 \times 1$

$\Rightarrow a^{2}+b^{2}=1-2=-1$

$\Rightarrow a^{2}+b^{2}=-1$