代数式x2+x+3的值为7,则3x2+3x+7的值为_______.

代数式x2+x+3的值为7,则3x2+3x+7的值为_______.
代数式x2+x+3的值为7,则3x2+3x+7的值为_______.

代数式x2+x+3的值为7,则3x2+3x+7的值为_______.
x2+x+3=7
x2+x=4
3x2+3x+7
=3（x2+x）+7
=3*4+7
=19

∵ x ² + x + 3 = 7
x ² + x = 7 - 3
x ² + x = 4
∴ 3 x ² + 3 x + 7 = 3（x ² + x）+ 7
= 3 ×...

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∵ x ² + x + 3 = 7
x ² + x = 7 - 3
x ² + x = 4
∴ 3 x ² + 3 x + 7 = 3（x ² + x）+ 7
= 3 × 4 + 7
= 12 + 7
= 19



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3x2+3x+7=3x²+3x+9-2=3(x²+x+3)-2=21-2=19
代数式x²+x+3的值为7