task/30311651 Упростите выражение
3) (2c+3)(3c+2) - (2c +7)(2c -7) =6c² +<u>4c</u>+<u>9c</u> +6 - (4c²- 49) =
<u>6c</u>² +13c + <u>6</u> - <u>4c</u>² + <u>49</u> = 2c² +13c +55 . * * * (a+b)(a-b) = a² - b² * * *
4) (3d +5)(5d - 1) - (6d - 3)(2 - 8d) = (3d +5)(5d - 1) + (6d - 3)(8d -2) =
15d²- <u>3d</u> +<u>25d</u> -5 +48d² -<u>12d </u>- <u>24d</u> + 6 = 63d² - 14d + 1 .
7tg30° * ctg30° = 7(tg30° *ctg30°)= 7*1=7
<span>sin^2 (18)-cos^2(18)=-cos(36)=-cos(90-54)=-sin(54). Это числитель.</span>
<span>sin^2 (117)=sin^2 (90+27)=сos^2 (27)</span>
<span>10*tg(27)*сos^2 (27)=10sin (27)сos(27)=5sin(54). Это знаменатель.</span>
<span>(-sin(54))/(5sin(54))=-1/5</span>