x-5=2√6
x²-10x+25=24
x²-10x+1=0
3倍x的四次方—28倍x的三次方—17倍x的二次方+2x—10
=3x^4-30x³+3x²+2x³-20x²+2x-10
=3x²(x²-10x+1)+2x(x²-10x+1)-10
=-10