Đáp án:
Giải thích các bước giải:
{S=−14P=−101{S=−14P=−101
⇔⇔{x1+x2=−14x1.x2=−101{x1+x2=−14x1.x2=−101 Xét
A=x1x2(1−x2)+x2x1(1−x1)A=x1x2(1-x2)+x2x1(1-x1)
=x1x2−x1+x2x1−x2=x1x2-x1+x2x1-x2
=(x1x2+x2x1)−(x1+x2)=(x1x2+x2x1)-(x1+x2)
=x21+x22x1.x2−(x1+x2)=x12+x22x1.x2-(x1+x2)
=(x1+x2)2−2x1.x2−101−(−14)=(x1+x2)2-2x1.x2-101-(-14)
=(−14)2−2.(−101)−101+14=(-14)2-2.(-101)-101+14
=−32331616+14=-32331616+14
=−129316464