全品七下P27答案

全品

$1.A\\ 2.1,0\\ 3.C$
$4.(1)\because~0.8^2=0.64,\\ \therefore~\sqrt{0.64}=0.8;\\ (2)\because~(\frac3{4})^2=\frac9{16},\\ \therefore~\sqrt{\frac9{16}}=\frac34;\\ (3)(-3)^2=9.\\ \because~3^2=9,\\ \therefore~\sqrt{9}=3;\\ (3)2\frac14=\frac94.\\ \because~(\frac32)^2=\frac94,\\ \therefore~\sqrt{2\frac14}=\frac32.$
$5.(1)\ge;(2)\ge,非负数.$
$6.A\\ 7.C\\ 8.A\\ 0的算术平方根还是0，即\sqrt{0}=0；\\ 1的算术平方根还是1，即\sqrt{1}=1；\\ -1没有算术平方根.\\ 9.A\\ 10.D\\ 11.a^2+8\\ 思路：\sqrt{x}=a,x+8=?\\ 12.2,\sqrt{5}$
$13.解：设每块正方形地板砖的边长为x~m,\\ 则~25x^2=9,\\ x^2=\frac9{25}.\\ 因为~x>0, 所以~x=\sqrt{\frac9{25}}=\frac35.$
$14.解：\sqrt{2a+1}=0,\sqrt{b-a}=\frac12,\\ 2a+1=0,b-a=\frac14,\\ a=-\frac12,b=-\frac14.\\ \therefore~\sqrt{\frac12 ab}=\sqrt{\frac12\times(-\frac12)\times(-\frac14)}\\ =\sqrt{\frac1{16}}=\frac14.$