Question

Решите уравнение 7,8

Answer 1

$sqrt{34-5x}+2x=7\ sqrt{34-5x}=7-2x\ 34-5x=49-28x+4x^2\ 4x^2-23x+15=0\ x_1=5 \7-2times5<0\ x_2=frac{3}{4}\ 7-frac{3}{4}times2>0\ x=frac{3}{4}$

$2sin^22x+cos2x-1=0\ 2x=alpha \ sin^2beta =frac{1-cos2beta}{2} \ 1-cos2alpha +cosalpha-1=0\ cosalpha =cos2alpha \ cos2x=cos4x\ x=frac{pi k}{3}$