<span>4n-m 3m+n 12mn-3m^2-12mn-4n^2 -3m^2-4n^2
--------- ---------= ---------------------------------- =------------------
20mn² - 15m²n 60m^2n^2 60m^2n^2
</span>
<span> 8 8+x^3-2x^2+2x^2-4x+4x-8 x^3
---- </span><span>+ x² + 2x + 4=------------------------------------------------</span>=--------
<span>x-2 x-2 x-2
</span>b+3 b-1 b+3 b-1 b^2+3b-9b+9 <span>(b-3)^2</span> b-3
------ ------- =-------------- - ---------------= ---------------------=----------------------=---------
9b-27 - b² - 3b 9(b-3) b(b-3) 9b(b-3) 9b(b-3) 9b
{x-y=18
{x²-y²=432
По формуле разности квадратов:
x²-y²=(x-y)(x+y)
x-y=18
тогда
x²-y²=18(x+y)
{x-y=18
{18(x+y)=432
{x-y=18
{x+y=24
Складываем
2х=42
х=21
у=х-18=21-18=3
О т в е т . 21 и 3
1)сosa=-√1-0,36=-0,8
2sinacosa+cos²a-sin²a=2*(-0,8)*(-0,6)+(-0,6)²-(-0,8)²=0,96+0,36-0,64=0,68
2)cosa=√1-0,64=0,6
cos²a-sin²a+6sina/cosa=0,36-0,64+6*(-0,8)/0,6=-0,28-8=-8,28
3)sin(π/4-a)=sinπ/4cosa-cosπ/4sina=√2/2(cosa-sina)=√3/8⇒ cosa-sina=√3/8:1/√2=√3/8*√2=√6/8
(cosa-sina)²=cos²a+sin²a-2cosasina=1-sin2a=(√6/8)²=6/64=3/32⇒
sin2a=1-3/32=29/32
4)cos(a+π/4)=cosacosπ/4-sinasinπ/4=√2/2(cosa-sina)=√5/8⇒ cosa-sina=√5/8:1/√2=√5/8*√2=√10/8
(cosa-sina)²=cos²a+sin²a-2cosasina=1-sin2a=(√10/8)²=10/64=5/32
sin2a=1-5/32=27/32