Question

Clare buys some shares for $50x. Later, she sells the shares for $(600 + 5x). She makes a profit of 2%

It can be shown that x² + 90x – 1200 = 0
Solve x² + 90x – 1200 = 0
Find the value of x correct to 3 significant figures

Answer 1

By applying the quadratic formula to the given equation x² + 90x – 1200 = 0, we find that the value of x correct to 3 significant figures is 11.79.

Step-by-step explanation:

To solve the quadratic equation x² + 90x – 1200 = 0, we can apply the quadratic formula, which is x = (-b ± √(b² - 4ac)) / (2a) where a, b, and c are the coefficients of the quadratic equation ax² + bx + c = 0. In this case, a = 1, b = 90, and c = -1200.

Using the quadratic formula:

x = (-(90) ± √((90)² - 4(1)(-1200))) / (2(1))
x = (-90 ± √(8100 + 4800)) / 2
x = (-90 ± √(12900)) / 2
x = (-90 ± 113.58) / 2

Thus, we have two possible solutions for x:

x = (-90 + 113.58) / 2 or x = (-90 - 113.58) / 2

x = 23.58 / 2 or x = -203.58 / 2

x = 11.79 (rounded to 3 significant figures) or x = -101.79 which doesn't make sense in this context since the value of x represents money and cannot be negative.

Therefore, the value of x correct to 3 significant figures is 11.79.