The answer is the third one.
The way I think through these problems is that where you multiply (-7x), you use addition, and where you use addition (-4), you multiply.
The answers added together will equal the second number, -7, and multiplied will give you the third, -4.
What you had chosen as the answer was close. But 7.53+-0.53 equals positive 7, not negative. However they do round to -4 when multiplied.
The correct answer, -7.53 and 0.53, do equal -7 when added together and equal -4 when multiplied.
You would probably need a little larger sample of people because not all people wear corrective lenses. In almost any other survey, this would be a scientist’s dream, but in this one, you’d need it to be a little bigger.
Answer:
C
Step-by-step explanation:
Its C because its x (a variable) and is costanly changing
If you expand out the brackets you get this,
(4+5i)(a+2i) = 4a + (5a)i + 8i - 10
The -10 comes from 5i * 2i.
Squaring i becomes -1.
Let's group the real stuff together,
and imaginary separately,
(4a - 10) + (5a + 8)i
For this to be purely imaginary,
the real part needs to be zero.
Therefore 4a - 10 = 0
Solve for a.
