<span>ax² +bx + c = a (x -x₁)(x - x₂)
1) 10х² + 29x - 30 = 10·(x -</span><span>(-29-√2041)/20 )·(x -</span><span><span>(-29+√2041)/20</span> )
D = 29²-4·10(-30)=841+1200=2041
x₁=(-29-√2041)/20 x₂=(-29+√2041)/20
2) 5х²- 30х + 35 = 5 ·( x -3+√2 )·(x - 3-√2)
D= (-30)²-4·5·35=900-700=200
</span>
x₁=(30-10√2)/10=3-√2 x₂=(30+10√2)/20=3+√2
A₂+a₈=5 ∑a₉ -?
a₁+d+a₁+7a=2a₁+8d=5
∑a₉=(a₁+a₉)*n/2=(a₁+a₁+8d)*9/2=(2a₁+8d)*4,5=5*4,5=22,5.
20/7=2.6/7
87/10=8.7/10
247/23=10.17/23
377/18=20.17/18
249/100=2.49/100