Question

$-4* \sqrt{49b^{-4}}+ \sqrt{81b^{-4}}++ \sqrt{144b^{-4} }$

Answer 1

$-4*\sqrt{49b ^{-4 } }+ \sqrt{81b ^{-4} } + \sqrt{144 b^{-4} }$
 $-4* \sqrt{7 ^{2} \frac{1}{b ^{4} } } + \sqrt{9 ^{2} \frac{1}{b ^{4} } } + \sqrt{12 ^{2} \frac{1}{b ^{4} } \fra}$  $-4* \frac{7}{b ^{2} } + \frac{9}{b ^{2} } + \frac{12}{b ^{2} }$ = $-4+ \frac{28}{b ^{2} }$ = $\frac{-112}{b ^{2} }$
                                     ............Kd