4х=-8+3у
х=-(8+3у):4
-3(8+3у):4-4у=-13
(-24+3у):4+13=4у
4у=(28+3у):4
13у=28
у=28:13
8. 4√2-3√8+2√32=4√2-2√4×2+2√16×2=4√2-6√2+16√2=14√2
(6sin²x+13sinx+5)·√(11·cosx)=0
1) 6sin²x+13sinx+5 = 0
D = 13² - 4·6·5 = 49
√D = 7
sinx₁ = (-13 - 7):12 = -20/17 < -1 (не может быть решением, т.к. E(sinx) =[-1; +1]
sinx₂ = (-13 + 7):12= -0.5
x₂ = (-1)^(k+1)· π/6 + πk, k ∈ Z
2) √(11·cosx) = 0
cosx = 0
x₃ = 0.5π +πn, n∈ Z
(х+2)(х-2)(х^2+4)-(4+х^2)^2=(х^2-4)(х^2+4)-(16+8х^2+х^4)=х^4-16-16-8х^2-х^4=-8х^2-32= -8(х^2+4)
Если х=1/2=0,5, то -8(х^2+4)=-8(0,5^2+4) =-8(0,25+4) =-8*4,25=-34