А)<span>4a²-9
б)</span><span>у²-25в²;
в)</span><span>у²-0,64х²;</span>
G ( 0 ) = V 0 = 0
g ( 1 ) = V ( 5 - 1 ) = 2
g ( 3 ) = V ( 15 - 9 ) = V 6
6.
sin51°cos39°-sin21°cos9°=sin(90°-39°)cos39°-sin21°cos9<span>°=
=cos39</span>°cos39°-sin(30°-9°)cos9°=cos²39°-sin(30°-9°)cos9<span>°=
=(cos(30</span>°+9°))² - (sin30°cos9°-cos30°sin9°)cos9<span>°=
=(cos30</span>°cos9°-sin30°sin9°)² - (¹/₂ cos9° - (√3/2) sin9°)cos9<span>°=
=((</span>√3/2) cos9° - ¹/₂ sin9°)² - ¹/₂ cos² 9° + (√3/2) sin9° cos9<span>° =
= </span>³/₄ cos² 9° - (√3/2)sin9° cos9° + ¹/₄ sin² 9° - ¹/₂ cos² 9° + +(√3/2)sin9°cos9<span>°=
= </span>³/₄ cos² 9° - ²/₄ cos² 9° + ¹/₄ sin² 9<span>° =
= </span>¹/₄ cos² 9° + ¹/₄ sin² 9<span>° =
= </span>¹/₄ (cos² 9° + sin² 9<span>°</span>)= ¹/₄ * 1 = ¹/₄
Обозначим искомое число как n
2n-12=3n-15
-12=n-15
+15-12=n-15+15
n=3
Ответ:3
1 (√3 - √7 )^2=(√3)^2-2√21 +(√7)^2=3-2√21 +7=10-2√21 ;
√24 √3
2 (3√24 + √3):√3 -3√2= (3 ------ + ------- ) -3√2 = (3√2*4 + 1) -3√2 = 7√2 - 3√2=
√3 √3
=4√2 ;