Answer:
1)
[tex]6x^2=-90\\x^2=-15\\\sqrt{x^2} =\sqrt{-15} \\x=i\sqrt{15} ,-i\sqrt{15}[/tex]
2)
[tex]b^2-4=-2\\b^2=2\\\sqrt{b^2} =\sqrt{2} \\b=\sqrt{2} ,-\sqrt{2}[/tex]
3)
[tex]16x^2-7=-6\\16x^2=1\\x^2=\frac{1}{16} \\\sqrt{x^2} =\sqrt{\frac{1}{16}} \\x=\frac{1}{4} ,-\frac{1}{4}[/tex]
4)
[tex]10p^2+9=239\\10p^2=230\\p^2=23\\\sqrt{p^2} =\sqrt{23} \\p=\sqrt{23},-\sqrt{23}[/tex]