Sin²a=1:(1+ctg²a)=1:(1+0,04)=25/26
sina=-5/√26
cosa=√(1-sin²a)=√(1-25/26)=1/√26
tga=1/ctga=-5
4х^2-16x=0
x(4x-16)=0
x=0 или 4х-16=0
4х=16
х=4
ответ: 0 и 4
√3·cos²15°- √3·sin²15°=<span>√3</span>·<span>(cos</span>²<span> 15°- sin</span>²<span> 15°) =</span>√3·сos(2·15⁰)=√3·cos30⁰=√3·√3/2=3/2=1,5
(4х + 3)(х-1) - (3х - 2)(х+2) = 10 - 5х
4х * х + 4х * (-1) + 3*х +3*(-1) - (3х*х + 3х*2 - 2*х -2*2) = 10 - 5х
4х² - 4х + 3х - 3 - (3х² + 6х - 2х - 4) = 10 - 5х
4х² - х - 3 - 3х² - 4х + 4 = 10 - 5х
х² - 5х + 1 = 10 - 5х
х² - 5х + 1 - 10 + 5х = 0
х² - 9 = 0
х² - 3² = 0
(х - 3)(х +3) = 0
х - 3= 0
х₁ = 3
х + 3 = 0
х₂ = - 3