Answer:
f(x) = x² - 2x - 15
Step-by-step explanation:
∵ The function intersect x-axis at -3 and 5
∴ f(x) = 0 at x = -3 , 5
∵ The form of the quadratic equation is ⇒ ax² + -b/a x + c/a = 0
ax² - b/a x + c/a = 0
Where the sum of its roots is b/a and their multiplication is c/a
∵ a = 1
∵ -3 , 5 are the roots of the quadratic equation
∴ b = -3 + 5 = 2
∴ c = -3 × 5 = -15
∴ f(x) = x² - 2x - 15
Check the picture below.
a) 1.3652
b) 1.3906
a) log5 9 = log5 3² = 2log5 3 = 2(0.6826) = 1.3652
b) log5 75/8 = log5 75 - log5 8 = log5 3×25 - log5 8=
log5 3 + log5 5² - log5 8 = 0.6826 + 2 - 1.2920 = 0.6826 + 0.708 = 1.3906
