20-20х-120=420
-20х=420-20+120
-20х=520
х=520/-20
х=-26
А) у,4х^2, 8ху
б) 4, 9у^2, 16
в) 2n, 8mn , 4m^2
г) а, 3, 6а
Cosx = - √3/2
x = (+ -)*arccos(-√3/2) + 2πn, n∈Z
x = (+ -)*(π - arccos(√3/2)) + 2πn, n∈Z
x = (+ -)*(π - π/6) + 2πn, n∈Z
x = (+ -)*(5π/6) + 2πn, n∈Z
А)72*3-44*3=84. 84:7=12
б)215*3+94*3=927. 927:3=309
<em>a</em>4<span> = </span><em>a</em>3<span> • </span><em>q</em><span> = (</span><em>a</em>1<span> • </span><em>q</em>2<span>) • </span><em>q</em><span> = </span><em>a</em>1<span> • </span><em>q</em>3