√8x - 15x² - 1 = 0
- 15x² + 8x - 1 = 0²
15x² - 8x + 1 = 0
D = b² - 4ac = ( - 8)² - 4 × 15 × 1 = 64 - 60 = 4 = 2²
x₁ = 8 + 2 / 30 = 10 / 30 = 1/3
x₂ = 8 - 2 / 30 = 6 / 30 = 1 / 5
7π/2 < 12 < 4π ⇒ 12 ∈ ④
-π < -3π/4 < -π/2 ⇒ -3π/4 ∈ ②
π/2 < 2.5 < π ⇒ 2.5 ∈ ②
-0,1х(10х^2+30-8х^4-24х^2)=-х^3-3х+0,8х^5+2,4х^3=1,4х^3-3х+0,8х^5=0,8х(1,75х^2-3,75+х^4)
10 × √0.25 + 1 ÷ 26 × √169 =10*0,5 + 1÷ 26 × 13 = 5+ 1/2 = 5,5