0.4x=0.4-2x+2
0.4x+2x=0.4+2
2.4x=2.4
x=1
Смотри решение во вложении
B1+b1q²=15⇒b1(1+q²)=15⇒1+q²=15/b1
b1q+b1q³=30=b1q(1+q²)=30⇒b1q*15/b1=30⇒15q=30⇒q=2
b1=15/(1+q²)=15/(1+4)=15/5=3
4x^2 - 17x + 15 ≥ 0
4x^2 - 17x + 15 = 0
D = 49 = 7^2
x1 = (17 + 7)/8 = 3;
x2 = (17 - 7 )/8 = 5/4 = 1,25
+ - +
----------- 5/4 ------------ 3 ----------> x
x ∈ ( - ∞; 1,25] ∪ [3; + ∞)