Question

(7х-9)(7х+9)-49*х²+7х+20 при х=90 1 569 2 573 3 560 4 564

Answer 1

Ответ:

569

Пошаговое объяснение:

(7х-9)(7х+9)-49*х²+7х+20

49*х²-81- 49*х² +7x+20

7x-61

90*7-61=630-61=569

Answer 2

To evaluate the expression (7x-9)(7x+9)-49x²+7x+20 when x=90, we substitute x=90 into the expression and perform the calculations.

Let's substitute x=90 into the expression:

(7x-9)(7x+9)-49x²+7x+20 = (790-9)(790+9)-4990²+790+20 = (630-9)(630+9)-49*8100+630+20 = (621)(639)-396900+630+20 = 396819-396900+630+20 = -81+630+20 = 569

Therefore, when x=90, the expression (7x-9)(7x+9)-49x²+7x+20 equals 569.