Question

When the quadratic equation y = (x − 5)(2x + 3) is written in standard form, what is the value of the coefficient "b"?

Answer 1

Do you know the standard form of a quadratic?

Answer 2

nope, im completly hopeless when it comes to math in general @Julian101

Answer 3

OK, well, let's see if we can get you a step further away from the hopeless stage.

Answer 4

What if you multiply your two bracketed expressions together?

You use your FOIL method to get 2x^2 - 7x - 15

Do you understand this step?

Answer 5

I should have written it 2x^2 + 3x - 10x -15, so as not to skip a step, but it's the same thing.

Answer 6

Are you still there?

When the book says "standard form of the quadratic", it's referring to the form

y = ax^2 + b^x + c, which is just another way of writing the quadratic. a, b, and c are just whatever constants, or "coefficients" happen to be in front of the variable x.

The way the question is stated, that would be called "factored form".

Standard form makes it easier to use the quadratic formula to find the factors. In your question, standard form is

y= 2x^2 -7x-15

"b" is -7, that is, the number in front of x. "a" is 2, (the number in front of x^2, and "c", the number on its own, is 15.