[Toán 8] tìm ẩn phương trình

I

iceghost

$(x+6)^4 + (x+8)^4 = 16$
Đặt $t= x+7$
pt $\iff (t-1)^4 + (t+1)^4 = 16 \\
\iff 2t^4+12t^2+2 = 16 \\
\iff t^4+6t^2-7 = 0 \\
\iff (t+1)(t-1)(t^2+7) =0 \\
\iff \left[ \begin{array}{l} {}
t=-1 \\
t=1 \\ \end{array} \right. \\
\implies \left[ \begin{array}{l} {}
x+7=-1 \\
x+7=1 \\ \end{array} \right. \\
\iff \left[ \begin{array}{l} {}
x=-8 \\
x=-6 \\ \end{array} \right.$
 
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