Question

Раскройте скобочки 15-(7a+(4a-(a- найдите не известное число x: 5: 4x=1: 2

Answer 1

15-(7a+(4a-(a-9)))=15-(7a+(4a-a+9))=15-(7a+4a-a+9)=15-7a-4a+a-9=6-10а

x:5:4x=1:2
$\frac{x}{ \frac{5}{4x}}= \frac{1}{2} \\ {x}: \frac{5}{4x} =\frac{1}{2} \\ x* \frac{4x}{5}=\frac{1}{2} \\ \frac{4x^{2}}{5}=\frac{1}{2} \\ 8x^{2}=5 \\ x^2= \frac{5}{8} \\ x=+- \sqrt{ \frac{5}{8} } \\ x=+- \frac{ \sqrt{5}}{ \sqrt{8}} \\x=+- \frac{ \sqrt{5}}{ \sqrt{4*2}} \\ x=+- \frac{ \sqrt{5}}{2 \sqrt{2}} \\ x=+- \frac{ \sqrt{5}*2\sqrt{2}}{2\sqrt{2}*2\sqrt{2}} \\ x=+- \frac{ \sqrt{5*2}*2}{2*2\sqrt{4}} \\ x=+-\frac{2\sqrt{10}}{4*2}} \\ x=+-\frac{ \sqrt{10}}{4}$