Answer
$7.69x^2-1.26x+5.3
$
Work Step by Step
Removing the parenthesis and then combining like terms, the given expression, $
(1.29x-5.68)+(7.69x^2-2.55x+10.98)
,$ is equivalent to
\begin{array}{l}\require{cancel}
1.29x-5.68+7.69x^2-2.55x+10.98
\\=
7.69x^2+(1.29x-2.55x)+(-5.68+10.98)
\\=
7.69x^2-1.26x+5.3
.\end{array}
Let
\begin{array}{l}\require{cancel}Y_1=
(1.29x-5.68)+(7.69x^2-2.55x+10.98)
,\\Y_2=
7.69x^2-1.26x+5.3
.\end{array}
Using a graphing calculator, the graphs of $Y_1$ (dotted graph) and $Y_2$ (solid graph) are shown below. Since the graphs overlap, then $Y_2$ is the correct simplification of $Y_1.$
