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It is proved that the value of polynomial-2x ^ 2-8x-10 is always less than 0 no matter what the value of X is
-2x^2-8x-10=-(x^2+2x+1+x^2+6x+9)=-(x+1)^2-(x+3)^2
N ^ 2 is always greater than zero, so - n ^ 2 is always less than zero
The question is as follows: try to explain: no matter what the real number x takes, the value of the algebraic formula - 2x ＾ 2 + 8x-15 is always negative, and find out when x takes what value, the value of the algebraic formula is the largest
- 2x ＾ 2 + 8x-15 = - 2 (X & ＾ 178; - 4x + 4-4) - 15 = - 2 (X-2) & ＾ 178; + 8-15 = - 2 (X-2) & ＾ 178; - 7 ∵ - 2 (X-2) & ᦇ 178; ≤ 0 ＾ - 2 (X-2) & ᦇ 178; - 7 ≤ - 7 ＾ no matter what the value of real number x is, the value of algebraic formula - 2x ＾ 2 + 8x-15 is always negative, and the maximum value of algebraic formula is - 7 when x = 2
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