13 000, 426 000, 215 000, 531 000.
L₁ = 2πR₁ = 6,28 * 2 4/9 = 6,28 * 22 : 9 ≈ 15,35
L₂ = 2πR₂ = 6,28 * 2 = 12,56
L₃ = 2πR₃ = 6,28 * 4/9 ≈ 2,79
L₄ = 2πR₄ = 6,28 * (2 : 4/9) = 6,28 * 2 * 9/4 = 6,28 * 4,5 = 28,26
1) 2,4*47/12-2,25:11/8=0,2*47-18/11=94/10-18/11=(1034-180)/110=854/110=427/55=7 42/55
2)0,5*2/(0,5-2)= -1/1,5= -10/15= -2/3
3) -2⁴*3*7⁰=16*3*1=48
4) (7х+2у)²=49х²+28ху+4у²