if x is real , find the maximum value of the expression - 2 x ^ 2 + 7 x + 9 .
"this is an equation of a downward facing parabola . the maximum value is the top point of the parabola . - 2 x ^ 2 + 7 x + 9 = ( - 2 x + 9 ) ( x + 1 ) the roots are 9 / 2 and - 1 . the maximum value must be when x is halfway between these two points . x = 1.75 the maximum value is - 2 ( 1.75 ) ^ 2 + 7 ( 1.75 ) + 9 = 15.125 the answer is d ."
subtract(add(multiply(7, divide(multiply(2, 2), 7)), 9), multiply(2, power(divide(multiply(2, 2), 7), 2)))