X²-14x+24=0
{x₁x₂=24 x₁=12
{x₁₊x₂=14 x₂=2
по теореме виета
или
D=(-7)²((b/2)²)-24
D=25
x₁,₂=-(b/2)⁺₋√D
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a
x₁,₂=7⁺₋√25
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1
x₁=7+5=12 x₂=7-5=2
по дискриминанту
1, 2, 3, ..., 150
a1 = 1
a2 = 2
d = a2 - a1 = 2 - 1 = 1
a150 = 150
S150 = (a1 +a150)*75 = 151*75 = 11325
Х²+15х+50=0
Д:225-4*50=25=5²
х½=-15±5/2=
х1=10
х2=5