1. sin 36° + sin 40° + sin 44° + sin 48°/2sin 88° cos 4°sin 42° 2. cos16°-cos24°-cos32°+cos40°/cos86°sin8°cos28°

Question

Алгебра: 1. sin 36° + sin 40° + sin 44° + sin 48°/2sin 88° cos 4°sin 42° 2. cos16°-cos24°-cos32°+cos40°/cos86°sin8°cos28°​

monkeyone · Accepted Answer

1) 2х⁴+3х³-8х²-12х=0
х³(2х+3)-4х(2х+3)=0
(2х+3)(х³-4х)=0
х(х²-4)(2х+3)=0
х(х-2)(х+2)(2х+3)=0
х=0 х-2=0 х+2=0 2х+3=0
х=2 х=-2 2х=-3
х=-1,5
ответ: -2; -1,5; 2; 2.

2) 5х³+3х²-5х-3=0
х²(5х+3)-(5х+3)=0
(5х+3)(х²-1)=0
(5х+3)(х-1)(х+1)=0
5х+3=0 х-1=0 х+1=0
5х=-3 х=1 х=-1
х=-0,6
ответ: -1; -0,6; 1.

3) х⁴+2х³+2х²+2х+1=0
(х⁴+2х²+1)+(2х³+2х)=0
(х²+1)²+2х(х²+1)=0
(х²+1)(х²+1+2х)=0
(х²+1)(х²+2х+1)=0
(х²+1)(х+1)²=0
х²+1=0 (х+1)²=0
х²=-1 х+1=0
нет решений х=-1
ответ: -1.

1. sin 36° + sin 40° + sin 44° + sin 48°/2sin 88° cos 4°sin 42° 2. cos16°-cos24°-cos32°+cos40°/cos86°sin8°cos28°​

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