Perform the indicated operation and write the result in the form a + bi.
X^4+7x^2-18=0

How to do this , and can some one explain

Right triangle xyz has a right angle at vertex y and a hypotenuse that measures 24 cm. angle zxy measures 70º. what is the length of line segment xy? round to the nearest tenth. 8.2 cm 8.7 cm 22.6 m 25.5 cm

Find two numbers if their sum is 91 and the ratio is 6: 7?