Question

If g(x) = 2x2 + bx + 5 and g(1) = 4, what is the value of g(-1)?

Answer 1

Substitute for the values of x and then, solve the equation so using one another.

Answer 2

I am going to assume that this is a polynomial equation and "2x2" means 2 to the 2nd power judging by the use of g(x) by tendencies of math teachers.

If this is the case:

g(1) = 2(1 * 1) + 1b + 5 = 2 + 1b + 5 = 1b + 7
If g(1) = 4, then 1b + 7 = 4.

1b + 7 = 4

Subtract 7 from both sides

1b = -3

b = -3

g(-1) = 2(-1 * -1) + -1b + 5 = 2 - 1b + 5 = -1b + 7

Now substitute b for "-3" and you will get -1(-3) + 7 = 3 + 7 = 10.

g(-1) will equal 10.