Question

Can someone explain this to me ?

Answer 1

Suppose you had f=6, g=2, h=3 and you were asked to find

f - g - h

You would do it by substituting the given values for the letters to get

6 - 2 - 3

And this can be simplified to

1

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The question at hand is basically the same. You are given values of f(x), g(x), h(x) and asked to find their signed sum.

f(x) - g(x) - h(x)

= (3x+5) - (4x²-2) - (x²-3x+1) . . . . substitute the given values

= 3x + 5 - 4x² + 2 - x² + 3x - 1 . . . use the distributive property to eliminate parentheses. A minus sign in front changes the sign of every term inside parentheses.

= x²(-4-1) +x(3+3) +(5+2-1)

= -5x² + 6x + 6 . . . . . . collect terms . . . . matches the first choice