Решите по матану, пожалуйста: sin(x/4) + cos(x/4) = 1 cos6x - 2sin(3pi/2 + 2x) и если можно вот это :( 3x49^x - 16x21^x + 21x9^x меньше 0

1 2sin(x/8)cos(x/8)+cos²(x/8)-sin²(x/8)-sin²(x/8)-cos²(x/8)=0 2sin(x/8)cos(x/8)-2sin²(x/8)=0 2sin(x/8)*(cos(x/8)-sin(x/8))=0 sin(x/8)=0⇒x/8=πn.n∈z⇒x=8πn,n∈z cos(x/8)-sin(x/8)=0/cos(x/8) 1-tg(x/8)=0⇒tg(x/8)=1⇒x/8=π/4+πk.k∈z⇒x=2π+8πk,k∈z 2 cos6x+2cos2x=0 4cos³2x-3cos2x+2cos2x=0 4cos³2x-cos2x=0 cos2x(4cos²2x-1)=0 cos2x=0⇒2x=π/2+πn,n∈z⇒x=π/4+πn/2,n∈z 4cos²2x-1=0 4(1+cos4x)/2=1 1+cos4x=1/2 cos4x=-1/2 4x=+-2π/3+2πk,k∈z x=+-π/6+πk/2,k∈z 3 3*7^2x-16*7^x*3^x+21*3^2x<0/3^2x 3(7/3)^2x-16*(7/3)^x+21<0 (7/3)^x=a 3a²-16a+21<0 D=256-252=4 √D=2 a1=(16-2)/6=7/3 a2=(16+2)/6=3 7/3