<span>1)
</span>9х²-12х+5 = ((3х)² - 2·3х·2+2²) - 2² + 5 = (3х-2)²+1<span>;
65+16с</span>² +с⁴ = с⁴+16с+65 = ((с²)² + 2·с²·8 + 8²)-8²+65 = (с²-8)² -64+65=
= (с²-8)²+1<span>;
4а</span>² – 40а + 1 = ((2а)² - 2·2а·10+10²)-10²+1 = (2а-10)² - 100+1=(2а-10)²-99.
<span>
m</span>² +5mn + n² = (m²+2mn+n²) - 2mn+5mn = (m+n)²+3mn.
<span>
х</span>² - 6ху+у² = (x²-2xy+y²)+2xy-6xy = (x-y)² - 4xy.
<span>
9а</span>²+7аb+4b² = ((3a)²+2·3a·2b+(2b)²) -12ab+7ab = (3a+2b)²-5ab.
<span>
2)
• (5а— 3b) + (6b – 7b+4c) = </span>5а— 3b + 6b – 7b+4c = 5a - 4b + 4c.
<span>
• (6у – 8x+9z) – (11z – 13х + 4у) = </span>6у – 8x+9z – 11z + 13х - 4у =
<span>= 5x + 2y - 2z.
• 3х(5х – у) – 5у(2у-7х) = </span>15x² – 3xу – 10y² + 35xy = 15x²+32xy-10y².
<span>
• (7a – 9b)(4b + 3a) = 28ab-36b</span>²+21a²-27ab = 21a²+ab-36b².
<span>
• (7m –10)(2 – 9m) = 14m-20-63m</span>²+90m = -63m²+104m-20.
<span>
• (3c – 4b) = 3c - 4b.</span>
Ответ:
(1+2/3)•(1+2/5)•(1+2/7)•(1+2/9)•(1+2/11)•(1+2/13)=1 целая 2/3•1 целая 2/5•1 целая 2/7•1 целая 2/9•1 целая 2/11•1 целая 2/13=5/3•7/5•9/ 7•11/9•13/11•15/13=15/3=5
Объяснение:
Надеюсь помог вам.
5(2cos²x-1)-2cosx-3=0 10cos²x-2cosx-8=0 Замена а=cosx, 10а²-2а-8=0 5а²-а-4=0 D=1+80=9² a1=(1-9)/20=-8/20=-2/5=-0.4 a2=(1+9)/20=1/2 x=±arccos(-0.4)+2πn, n∈Z; x=±π/3+2πn, n∈Z;
