How do you find the zeroes for #f(x) = x^2 – 9x – 70#?

2 Answers
Mar 28, 2018

Answer:

#x=-14# and #x=5#

Explanation:

We need to think of two numbers, that, when I add them, sum up to #-9#, and when I multiply them, have a product of #-70#. Since the product is negative, we know the signs must be different.

Through some thought, we arrive at #-14# and #5# as our two numbers, because

#-14+5=-9# and

#-14*5=-70#

Thus, our equation is as follows:

#(x-14)(x+5)=0#

To find the zeroes, we take the opposite signs to get

#x=14# and #x=-5#

Hope this helps!

Mar 29, 2018

Answer:

-5 and 14

Explanation:

#f(x) = x^2 - 9x - 70 = 0#
To solve f(x), find 2 numbers (real roots) knowing the sum (-b = 9) and the product (c = - 70). They are: - 5 and 14.

Note . This method avoids proceeding the lengthy factoring by grouping and solving the 2 binomials.