Question

计算题√8+(1/2)^-1-4cos45°-2÷1/2*2

Answer 1

解

原式

=2√2+2-4×(√2/2)-2×2×2——最后面是2÷1/2再乘以2吗

=2√2+2-2√2-8

=-6

x²+2x-15=0

x²+2x=15

(x-2)/(x²-x)÷[(x+1)-3/(x-1)]

=(x-2)/x(x-1)÷[(x²-1)-3]/(x-1)

=(x-2)/x(x-1)×(x-1)/(x-2)(x+2)

=1/x(x+2)

=1/(x²+2x)

=1/15