Question

Помогите решить срочно!!!

Answer 1

1.
2cos²α-8sin²α=2(1-sin²α)-8sin²α=2-2sin²α-8sin²α=2-10sin²α
2-10*(0.3)²=2-10*0.09=2-0.9=1.1

2.
$7*20^{log_{20}3}-10log_{0.5} frac{1}{4}= \ =7*3-10log_{ frac{1}{2} }( frac{1}{2} )^2= \ =21-10*2log_{ frac{1}{2} } frac{1}{2}= \ =21-10*2=21-20=1$

3.
$( frac{1}{5} )^{3-2x}- frac{1}{625} geq 0 \ \ ( frac{1}{5} )^3*( frac{1}{5} )^{-2x}- frac{1}{125}* frac{1}{5} geq 0 \ \ frac{1}{125}(( frac{1}{5} )^{-2x}- frac{1}{5} ) geq 0 \ \ ( frac{1}{5} )^{-2x}- frac{1}{5} geq 0 \ \ ( frac{1}{5} )^{-2x} geq (frac{1}{5})^1 \ \ -2x leq 1 \ x geq -0.5$
x∈[-0.5; +∞)