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Bài 2:$P(1)=1+a+b+c+d+e=1$ $(1)$$P(2)=2^5+2^4a+2^3b+2^2c+2d+e=4$ $(2)$$P(3)=3^5+3^4a+3^3b+3^2c+3d+e=9$ $(3)$$P(4)=4^5+4^4a+4^3b+4^2c+4d+e=16$ $(4)$$P(5)=5^5+5^4a+5^3b+5^2c+5d+e=25$ $(5)$Lấy $P(5)-2P(3)+P(1)$ $P(4)-P(3)-P(2)+P(1)$ $P(3)-2P(2)+P(1)$ $\begin{cases}5^5-2.3^5+1+(5^4-2.3^4+1)a+...+(5^2-2.3^2+1)c=8 \\ 4^5-3^5-2^5+1+(4^4-3^4-2^4+1)a+...+(4^2-3^2-2^2+1)c=4 \\ 3^5-2.2^5+1+(3^4-2.2^4+1)a+...+(3^2-2.2^2+1)c=2 \end{cases}$$\Leftrightarrow \begin{cases} 464a+72b+8c=-2632 \\ 160a+30b+4c=-746 \\ 50a+12b+2c=-178 \end{cases}$$\Rightarrow \begin{cases}a=-15 \\ b=85 \\ c=-224 \end{cases}\Rightarrow \begin{cases}e+d=154 \\ e+2d=428 \end{cases}\Rightarrow \begin{cases}e=-120 \\ d=274 \end{cases}$

Bài 2:$P(1)=1+a+b+c+d+e=1$ $(1)$$P(2)=2^5+2^4a+2^3b+2^2c+2d+e=4$ $(2)$$P(3)=3^5+3^4a+3^3b+3^2c+3d+e=9$ $(3)$$P(4)=4^5+4^4a+4^3b+4^2c+4d+e=16$ $(4)$$P(5)=5^5+5^4a+5^3b+5^2c+5d+e=25$ $(5)$Lấy $P(5)-2P(3)+P(1)$ $P(4)-P(3)-P(2)+P(1)$ $P(3)-2P(2)+P(1)$ $\begin{cases}5^5-2.3^5+1+(5^4-2.3^4+1)a+...+(5^2-2.3^2+1)c=8 \\ 4^5-3^5-2^5+1+(4^4-3^4-2^4+1)a+...+(4^2-3^2-2^2+1)c=4 \\ 3^5-2.2^5+1+(3^4-2.2^4+1)a+...+(3^2-2.2^2+1)c=2 \end{cases}$$\Leftrightarrow \begin{cases} 464a+72b+8c=-2632 \\ 160a+30b+4c=-746 \\ 50a+12b+2c=-178 \end{cases}$$\Rightarrow \begin{cases}a=-15 \\ b=85 \\ c=-224 \end{cases}\Rightarrow \begin{cases}e+d=154 \\ e+2d=428 \end{cases}\Rightarrow \begin{cases}e=-120 \\ d=274 \end{cases}$$\Rightarrow \begin{cases}P(6)=156 \\ P(7)=769 \\ P(8)=2584 \\ P(9)=6801 \end{cases}$

Bài 2: $P(1)=1;P(2)=4;P(3)=9;P(4)=16;P(5)=25$$\Rightarrow $ có dạng tổng quát: $P(x)=x^2$$\Rightarrow P(6)=36;P(7)=49;P(8)=64;P(9)=81$

Bài 2:$P(1)=1+a+b+c+d+e=1$ $(1)$$P(2)=2^5+2^4a+2^3b+2^2c+2d+e=4$ $(2)$$P(3)=3^5+3^4a+3^3b+3^2c+3d+e=9$ $(3)$$P(4)=4^5+4^4a+4^3b+4^2c+4d+e=16$ $(4)$$P(5)=5^5+5^4a+5^3b+5^2c+5d+e=25$ $(5)$Lấy $P(5)-2P(3)+P(1)$ $P(4)-P(3)-P(2)+P(1)$ $P(3)-2P(2)+P(1)$ $\begin{cases}5^5-2.3^5+1+(5^4-2.3^4+1)a+...+(5^2-2.3^2+1)c=8 \\ 4^5-3^5-2^5+1+(4^4-3^4-2^4+1)a+...+(4^2-3^2-2^2+1)c=4 \\ 3^5-2.2^5+1+(3^4-2.2^4+1)a+...+(3^2-2.2^2+1)c=2 \end{cases}$$\Leftrightarrow \begin{cases} 464a+72b+8c=-2632 \\ 160a+30b+4c=-746 \\ 50a+12b+2c=-178 \end{cases}$$\Rightarrow \begin{cases}a=-15 \\ b=85 \\ c=-224 \end{cases}\Rightarrow \begin{cases}e+d=154 \\ e+2d=428 \end{cases}\Rightarrow \begin{cases}e=-120 \\ d=274 \end{cases}$