Jika (a - b) : (a + b) = 3 : 7 ,maka nilai dari (a² - b²) : (a² + b²) adalah A. 9 : 21 B. 2 : 13 C. 16 : 25 D. 21 : 29

[tex] \frac{a+b}{a-b} = \frac{3}{7} [/tex]

7a+7b=3a-3b

4a=-10b

a=[tex]- \frac{5}{2} [/tex]b

[tex]a^{2} - b^{2} = (a+b)(a-b)[/tex]

[tex]a^{2} - b^{2} = (-\frac{3}{2}b)(-\frac{7}{2}b)[/tex]

[tex]a^{2} - b^{2} = \frac{21}{4}b^{2}[/tex]

[tex]a^{2} + b^{2} = (a+b)^{2} - 2ab[/tex]

[tex]a^{2} + b^{2} = (-\frac{3}{2}b)^{2} + 2\frac{5}{2}b·b[/tex]

[tex]a^{2} + b^{2} = \frac{9}{4}b^{2} + 5b^{2} [/tex]

[tex]a^{2} + b^{2} = \frac{29}{4}b^{2} [/tex]

Maka: [tex] \frac{a^{2}+b^{2}}{a^{2}-b^{2}} = \frac{21}{29} [/tex]

Dan jawabannya adalah D