Solving <span>8x-5y=10 for y helps us to identify the y-intercept:
-5y = -8x + 10. Dividing both sides by -5, we get (8/5)x -2. Therefore, y = (8/5)x - 2; the y-intercept is (0,-2).
The equation </span><span>-6x-7y=-6 can be solved for its slope in the same manner.
7y = -6x + 6; then y = (-6/7)x + 6/7. Its slope is -7/6. A line perpendicular to this line has slope equal to the negative reciprocal of -7/6, which is 6/7.
So, using the slope-intercept form, y = mx + b becomes y = (6/7)x -2.</span>
<span>25.7 years
The rule of 72 is a simple approximation on how long it will take to double your money. You simply divide 72 by the interest rate and you'll have your estimate on the number of years it will take. So
72 / 2.8 = 25.7 years.
To demonstrate that it's just an estimate, you can take the log of 2 and divide by the log of 1.028 to get the exact value. This far more complicated calculation gives the result of 25.1 years. And to be honest, the estimate of 25.7 years is more than close enough for such an quick and easy rule of thumb.</span>
Add like terms
2+4i +7 +11 i =
2+7 + 4i+11i =
9+15i
She earned 145$ a day because 725/5 is 145
