Question

tìm x trong tỉ lệ thức:   a/ x:0,16 = 9:x                                               b/\(\frac{72-x}{7}=\frac{x-70}{9}\)

Answer 1

a/ x:0,16 = 9:x hay \(\frac{x}{0,16}=\frac{9}{x}\)

=>x.x=0,16.9

=>x²=1,44

=>x²=(1,2)²

=>x=1,2 hoặc x=-1,2

b)\(\frac{72-x}{7}=\frac{x-10}{9}\)

=>(72-x).9=7.(x-10)

648-9x=7x-70

-9x-7x=-70-648

-16x=-718

x=44,875

Answer 2

a) x: 0,16 =9:x hay       \(\frac{x}{0,16}\)=\(\frac{9}{x}\)

\(\Rightarrow\)x.x= 0,16.9

\(\Rightarrow\)\(^{x^2}\)=1,44

\(\Rightarrow\)\(^{x^2}\)= \(^{\left(1.2\right)^2}\)

\(\Rightarrow\)x=1,2 hoặc -1,2.

b) \(\frac{72-x}{7}\)= \(\frac{x-10}{9}\)

\(\Rightarrow\)(72-x).9 = 7.(x-10)

648-9x=7x-70

-9x - 7x=-70-648

-16x=-718

\(\Rightarrow\)x= 44,875.

Answer 3

44,875