4

$\pm 4$

8

$\pm 8$

$a^2•a^5＝a^{10}$

$（a﹣b{）}^2＝a^2﹣b^2$

$\mathit{（﹣}3a^3{）}^2＝6a^6$

$﹣3a^{2}b+2a^{2}b\mathit{＝﹣}{a}^{2}b$

$7.05\times {10}^7$

$70.5\times {10}^8$

$7.05\times {10}^8$

$7.05\times {10}^9$

$a\le \frac{1}{4}$ 且 $a\ne ﹣2$

$a\le \frac{1}{4}$

$a＜\frac{1}{4}$ 且 $a\ne ﹣2$

$a＜\frac{1}{4}$